I’m confused what the use would be for this spell. It seems kind of pointless to me, besides using it to stop yourself from falling.

It is not meant to be ridden.  It is a magic platform that follows you.  It's primary purpose is to carry up to 500 lbs of loot, or perhaps some dead companions.  But there are  other creative uses for it.

The disk is immobile while you are within 20 feet of it. 

The real crux of this spell is the usage of the word "immobile" in this sentence. Because as per the definition this can be interpreted as either simply unmoving, or as unable to be moved. 
And I am fearful that it is the latter that was intended by WOTC Staff.

Mr. Chris Perkins answered a question here . Stating that the disk only moves when it's caster moves 20-feet away from it. Which means that it is immovable while the spellcaster that summoned it is within 20-feet of it. And it will only move to be closer to the caster not just unlock from its current spot to be moved around by another character.

Why the didn't just use the EXACT same spell from 3/3.5 is beyond me [see spoiler for 3/3.5 text]

I'm not sure how this spell can be useful other than as a levitating, flat-bed trailer.    Maybe to haul something, or someone over difficult terrain?    I'm sure there's a campagin somewhere that this was made for.

 

 

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spells are meant to do anything, if you can ride it and u want to there's nothing stopping you

Hey, it doesn't way it can't cause damage which some weaker/utility spells does....
So run towards someone and misty step as far behind them as you can, watch the disc come flying at ramming speed trying to keep that 20ft distance, soft bodies are unlikely to count as "obstacles" then.
(work likely work similarly with haste or expeditions retreat and such too with an acrobatics check to vault/leap over the enemys space)

Toss em up and it's a 1 hour hammock.

Also a kobold bed.

have a rogue stand on it and move them away from melee range of opponents while they use steady aim every round (the rogue is not using their own move and don't provoke opportunity attacks either)

stay at the back of the party, cast darkness on it and if the front line are attacked, take a step back... step forward, cast, step back... 

a ballista weighs about 200 lbs

Give this to an elf and you can travel during a long rest.

Give this to a Elf and you can suddenly travel whilst having a long rest

 (as long as you Jeep your equipment light)

@DLtheDM
Because of threads like these: https://forums.giantitp.com/showthread.php?372094-Floating-Disk-ongoing-debate

Tldr, the crux of the argument with the previous version is that "if not otherwise directed" implied the ability to be directed, that is intentionally moved in a specified direction within the spells ranges. Despite the spell not mentioning that as a function, and a FAQ sage advice post saying that it cannot be used that way. And a greater version of the spell adding the functionality of being directable implying that specific functionality is something the lesser spell lacks.

This is clear, at least on that point.

As an aside I see no problem with either interpretation. It's just a 1 inch wide disk of force that lasts for an hour, also requiring that the caster not move. Maybe you can block a narrow passageway for some sort of huge creature? You're still within 20 feet.

One of the issues here is the difference between RAW (Rules As Written) and Rules As Intended. If you've got nothing better or positive to do than twist the rules to be something other than intended, you're wasting your time and everyone else's.

I've run across poorly worded definitions in other versions of D&D and other games... mostly because the author never thought his words could be twisted into something he didn't intend.

I'd change the wording to say that the disc follows BEHIND you. But, that being said, I don't see any reason that the spell can't be tweaked to have other variations. In 3/3.5, this would be accomplished by Feats, particularly 3rd party publications that intentionally expanded the basic rule. For 5th, I'd go one of two ways.

1. For every wizard level about 1st (since you only have to be 1st level to cast the 1st level spell), you can tweak the parameters in one way.

2. Once you have enough experience in casting the basic spell, you've now learned how to tweak it to better suit your needs. Say, +5 wizard levels. Thus, at 6th level, you can tweak the spells parameters.

Some typical tweaks: you can direct it to move beside you, closer to you, farther away from you; you can change the shape from a flat surface to a concave disc to a floating wedge to a bowl or disc with a lip, to an 'I' shaped plane; you can make it go faster or slower; you can cause it to ram someone; you can ride on it by directing it to move while standing on it; you can shape it into a long narrow beam for crossing a 10' pit; etc. Keep in mind what's reasonable, not what you think is cool or possible.

1st mobile artillery?

2nd this isn't concentration so if you were stuck in a pit you could create a staircase of disks

I just realized that with the disk having a 3ft diameter you could theoretically create impervious cover when you're fighting in 2.5ft scale. If you're using a race 3ft or smaller you just walk under the Floating Disk, and unless the enemy puts over 500 lbs on it it won't break. Since there's nothing else about breaking or damaging it the disk is technically impervious to all forms of damage. At the very least you'd have anywhere from half to full cover while under it and most melee attackers would have to make themselves prone in order to actually have a clear shot at whoever was under the disk.

Ok.. here me out.

You are an Artificer,  you create (infusion) a  HOMUNCULUS SERVANT. You then pick up Spell Wrought Tattoo as a second infusion and store this spell in it.

You tattoo the HS.

It creates the disk, 

you jump on the disk.

The HS flyes to where you want it to do. You follow, at 10 ft high and 30 ft per round. Have a nap, make some coffee, let the HS do the driving.

Quote from ThrustBone >>

The disk is immobile while you are within 20 feet of it. If you stood on top of it like a skateboard you wouldn't be able to move. you'd need to construct some sort of apparatus or consider telepathic magic to control the disk but even then I think some dms would say no.

Can this spell be used in tandem with telekinesis? Like can you ride on top of it while moving it with your mind?

Quote from Akamoria >>

Can Floating Disk + Levitate make a makeshift elevator by targeting the disk?

They both have a weight limit of 500 pounds so I imagine it would work. Tenser's Floating Disk is a conjuration spell, so perhaps the disk would count as an "object" for the purposes of Levitate. Thoughts?

 The disk floats 3ft off the ground and can not move to a space that would make it be 10ft off the ground, so you can not make an elevator out of it or a flying chariot. 

Immovable. So the caster could not sit upon disk and move like a boat. Caster has to cross the river 20' away from the disk to ferry others across. 

Provided the phantom steed can cast the spell because the disk follows the caster 20' back.