ok for context my character chopped off the wongs of unconscious succubi in hopes to attach them to himself, what's an in-game mechanic that can make it work?
if it helps my character is a level 10 half-orc bard

Permanent flight by sewing dead body parts to you?  I don't think there is an actual mechanic in game for that exactly...

If I was DM'ing and I was willing to allow this (and I probably wouldn't) I would make this the end result of same wild and dangerous quests, not just something you could have a local tailor do with a needle and thread.  I mean ok, this is D&D and there is magic and all but you're basically asking how you can cut the wings off a bird and make them a working part of you.  That's not easy to do....

There is no in-game mechanic for Shou Tuckering yourself.  Most DMs wouldn't allow it, and if you pushed they'd probably say you end up disfiguring yourself for your efforts with no gain. If you want innate flight you need to find or create a magical item, or be one of the few classes that gets that ability at higher level. 

As mentioned, there's no hard/fast rules or mechanics to accomplish this. However....

This can be a conversation with the DM, to negotiate/compromise this possibility. For example, considering there are numerous different magic items (some attuned, some not) that either provide a permanent or temporary / has-charges ability for flight (or swimming, climbing movement speeds), if I'm your DM I'm willing to listen to any reasonable proposals from the player to reach the player's goal. 

For example, if you consider that wings & permanent flight is (for all intents and purposes in game mechanics) just another magic item, ask DM under what conditions your character can "Craft" these wings onto your body. It could be that it would take 4 weeks of downtime, could cost 2000 gp in other magic materials, and proficiency needed in Weaver's tools or Leathermaker's tools to construct the wings and/or graft them onto your own body.

It could even need the involvement of another party member who has the necessary tools proficiencies.

It's really a call, in my opinion, how creative one can be and how wiling a DM wants to be... very few things (in my opinion as a DM) should be impossible, but there should be a heavy time/cost investment to go along with it

 Edit: consult DMG and Xanathar's for more information/guidance on creating/crafting

Honestly, if they have the functionality of say....Winged Boots, I'd work out a way to meet with some unsavory NPC who would be willing to graft those wings to your character's body.  

Accomplishing something like this should be a process of long, painful magic rituals that require all sorts of unspeakable components, and if successful (there's no guarantee) you'll be facing long-term consequences for voluntarily grafting body parts from a fiend to yourself.

If your Dm says ok to giving yourself wings but wants a mechanic I made up a Wizard subclass for my own camapgin based around this sort of thing..

https://drive.google.com/file/d/1CDr1pG9J7SmIgGTvcqgzwVU3f0q4RPcp/view?usp=sharing

The Mutagenic Surgeon has a bunch of things you can get but there is always a risk and a large GP cost involved.

If this was in my game, I'd allow a character to use them as the primary component in crafting a pair of Wings of Flying. It's a rare item, so it would take 10 workweeks, 2,000gp in additional supplies, and require the player to either be proficient in a thematically appropriate tool (such as Weaver's Tools) or simply be proficient in Arcana. The time can be reduced if they work with another character... either another party member or they could hire a craftsman in-town to assist. If they're willing to eat the cost I'd also allow them to simply find a craftsman in-town to create it for them while they're busy adventuring.

Of course, Wings of Flying are simply the most visually appropriate statted item, since by RAW it produces large wings on the character's back... but only for 1 hour before needing to recharge. Ironically if you give them the stats of winged boots (as Metamongoose suggested), while the fly speed is much lower, it would perhaps fit the goal they're reaching for a bit more, since Winged Boots can be used much more casually... unless the character insists on flying as much as possible, they don't even really need to track the limits it has on the boots' flying time, since it's so rare to ever need to. This would also make it a lot easier to craft, since Winged Boots are considered an Uncommon item and thus would only take 2 workweeks and 200gp of ingredients to craft.