I am a new dm for a small group, 3-4 people, and I have no idea how I should start my campaign. I want it to have to do with an organization that is constructing some type of giant human body. If you can find some type of start or campaign idea, I thank you greatly.

Best,

GunlunDerby

You could for the giant human body use the flesh golem. Just an idea though. 

Also how most of my campaigns start are in cities so they can have someplace as an HQ.  

Start in a tavern!  :)

In this case, you could be in a larger town and perhaps your adventurers are party of an "occult club" tasked with tracking down and destroying such abominations. They have heard rumours of a necromancer/scientist/witch/whatever in some other area that may be constructing a franken-giant (or flesh golem).  It could even start more simply with parts disappearing from nearby graveyards....

Yes, starting in a tavern is classic for a reason. 
Are the players new, as well? If everyone is new, you might want to start with a published adventure. They can really help with structure and encounter balancing. 

So is the Human corpse monster the end of the campaign idea or the starting boss kinda thing? That makes a big difference to the answer that your going to get.

Starting area idea:

Graveyards, Church, Temple, Ancient Battle Ground/Fresh Battle Ground

Starting Quests:

Check out rumors of the things in the graveyard, Help find a hero's body on a battleground, Taking refuge in a church while living corpses attack

Hope this sorta helped

Guy from How To Be A Great GM (look him up on Youtube) has an amazing full series on crafting a campaign from scratch.

His key advice for starting a campaign is "the sentence"  : Someone wants something badly and is having trouble getting it. From there, fill in the who/what/when/where/why.

(BBEG necromancer) wants to (build a giant flesh golem) but is having trouble (constructing the parts) because (to build it as big as he wants, he'll need giant parts. Giants are notoriously hard to kill, even for seasoned mercenaries.)

So what's his plan?

Guy suggests building it around 4 arcs: getting stuff, building stuff, testing stuff, achieving stuff.

Getting stuff: This necromancer will need to acquire giant parts. To do so, he'll need to hire seasoned adventurers. If your party is starting at level 1, it'll be awhile before they're fit to hire for his plan. So maybe he starts off with smaller creatures to build a small army of flesh golems so he can send a lower-level group after a giant with an army of flesh golems. So maybe he starts with goblins.
1) The BBEG has put out a notice that there are some goblins terrorizing a nearby village that need slaying. The party responds to this ad, having no idea what the evil intent is behind all of this.
2) If the party questions the village, they'll find that the goblins, while a nuisance, maybe haven't actually been attacking as much as the ad says. Just on merchants traveling in and out. Still enough of a problem that they'd be glad to see the goblins gone.
3) Suppose the party attacks the goblins. The ad says to bring the bodies to a specific place to bury - this is where the BBEG will later send a minion to pick the bodies up in secret.
4) The BBEG attempts to build a test golem with goblin parts. This works, but with complications; the golem is imperfect, perhaps it needs a certain magical item to control its actions, like an amulet that the BBEG puts on it.
5) The BBEG needs an old book from someone in order to study how to perfect this magic. So he hires someone else to hire the PCs to acquire this book for him - always works through a proxy so that he never has to meet the PCs face to face, at least not yet.
6) The PCs acquire this book and are rewarded handsomely. When they get the book for the proxy NPC, the return to find the proxy NPC has a new quest for them - some problematic bandits or hobgoblins or low-level trolls are moving in where the goblins were before, and need to be taken out (or something like that) - this is the BBEG's plan to make the next stage of flesh golems, and he plans to test out the new method he'll find in that book. Which, if the PCs check out, is a book on necromancy (and if the proxy is questioned he'll say only that it's for his employer, who has made a lifetime of studying the subject in an academic sense).
7) The PCs yet again clear out another "infestation" and are told to bury the bodies in a specific place - which again, the BBEG will have someone fetch later. At any point if the PCs revisit these graves, they'll find them suspiciously looted of the bodies.
8) The BBEG is now trying to make more flesh golems. He's now working on having a small army.

So on and so forth, with other quests thrown in like some character arcs to keep things varied and to give the BBEG some time to work on his project in between adventures. When the party is strong enough, perhaps with some flesh golems to help, the BBEG will hire them to kill some trolls (again through a proxy, who will tell the party to expect "Strange Reinforcements" that they'll "know are the allies by the (necklace/amulet/circlet/whatever) they wear (which keeps them under control)). By this point, the party may be getting suspicious.

Know that it's very possible the party will hint onto things early and start trying to stop whoever is doing this, meaning the BBEG will have to hire a different group. He should also have other minions working under him doing various things, such as scouting out areas where more "problematic creatures" can be found that could be used for the flesh golem.

Best of luck!

It is the finishing boss

Quote from gamsii >>

Guy from How To Be A Great GM (look him up on Youtube) has an amazing full series on crafting a campaign from scratch.

His key advice for starting a campaign is "the sentence"  : Someone wants something badly and is having trouble getting it. From there, fill in the who/what/when/where/why.

(BBEG necromancer) wants to (build a giant flesh golem) but is having trouble (constructing the parts) because (to build it as big as he wants, he'll need giant parts. Giants are notoriously hard to kill, even for seasoned mercenaries.)

So what's his plan?

Guy suggests building it around 4 arcs: getting stuff, building stuff, testing stuff, achieving stuff.

Getting stuff: This necromancer will need to acquire giant parts. To do so, he'll need to hire seasoned adventurers. If your party is starting at level 1, it'll be awhile before they're fit to hire for his plan. So maybe he starts off with smaller creatures to build a small army of flesh golems so he can send a lower-level group after a giant with an army of flesh golems. So maybe he starts with goblins.
1) The BBEG has put out a notice that there are some goblins terrorizing a nearby village that need slaying. The party responds to this ad, having no idea what the evil intent is behind all of this.
2) If the party questions the village, they'll find that the goblins, while a nuisance, maybe haven't actually been attacking as much as the ad says. Just on merchants traveling in and out. Still enough of a problem that they'd be glad to see the goblins gone.
3) Suppose the party attacks the goblins. The ad says to bring the bodies to a specific place to bury - this is where the BBEG will later send a minion to pick the bodies up in secret.
4) The BBEG attempts to build a test golem with goblin parts. This works, but with complications; the golem is imperfect, perhaps it needs a certain magical item to control its actions, like an amulet that the BBEG puts on it.
5) The BBEG needs an old book from someone in order to study how to perfect this magic. So he hires someone else to hire the PCs to acquire this book for him - always works through a proxy so that he never has to meet the PCs face to face, at least not yet.
6) The PCs acquire this book and are rewarded handsomely. When they get the book for the proxy NPC, the return to find the proxy NPC has a new quest for them - some problematic bandits or hobgoblins or low-level trolls are moving in where the goblins were before, and need to be taken out (or something like that) - this is the BBEG's plan to make the next stage of flesh golems, and he plans to test out the new method he'll find in that book. Which, if the PCs check out, is a book on necromancy (and if the proxy is questioned he'll say only that it's for his employer, who has made a lifetime of studying the subject in an academic sense).
7) The PCs yet again clear out another "infestation" and are told to bury the bodies in a specific place - which again, the BBEG will have someone fetch later. At any point if the PCs revisit these graves, they'll find them suspiciously looted of the bodies.
8) The BBEG is now trying to make more flesh golems. He's now working on having a small army.

So on and so forth, with other quests thrown in like some character arcs to keep things varied and to give the BBEG some time to work on his project in between adventures. When the party is strong enough, perhaps with some flesh golems to help, the BBEG will hire them to kill some trolls (again through a proxy, who will tell the party to expect "Strange Reinforcements" that they'll "know are the allies by the (necklace/amulet/circlet/whatever) they wear (which keeps them under control)). By this point, the party may be getting suspicious.

Know that it's very possible the party will hint onto things early and start trying to stop whoever is doing this, meaning the BBEG will have to hire a different group. He should also have other minions working under him doing various things, such as scouting out areas where more "problematic creatures" can be found that could be used for the flesh golem.

Best of luck!

 Thank you very much, this idea is amazing! i hope I can run it w/ out my players getting completely sidetracked...