Thanks breh, I don't sample in FL Studio, I use an MPC Touch (had the Renaissance before). I pitch shift a sample (pitching a sample without changing its Bpm/tempo), then I make some slices, and after I make my slices, I convert it into a program and play them out on my pads. I then speed up the sample (transpose) and make a sequence. It's not really much to it, I just make slices out of parts I think I can make a sequence out of. It's more of using your ears and listening rather than using techniques.
My mentor NY Bangers (look him up), he samples straight from FL, I think he does it with Edison or slicex not sure which but his chops are always dope.
Example of his work:
My advice for sampling would be to first listen to the song/sound you will sample from completely (even if you already found a part you want to chop). There is always more parts you can piece together for a intro/outro hook/verse.
Try to pitch shift your sample if you can (not sure FL Studio can do it), but it skips having to later time stretch your samples if they play short on the Bpm you want to use.
Add a little reverb (20%) to your sample and a 1/4 echo delay. It gives the sample chops more ambience and life.
Add onto the sample with sounds from vsts if possible (meaning play sounds/instruments matching your sample if possible).
Sometimes you can play different parts of samples on top of each other on your sequence. Meaning place a high filter (remove all low end) off one of the sample sequences to play on top of the other. When done correctly, it can help make your sequences less repetitive. This is useful when throwing vocals from a sample onto your sequence.
Draw out an original baseline from your vst by temporarily placing a low end filter on your sample chops (removes high end, plays the sample like if it was a bass). This method helps you make a new matching bass line to your sample.
Throw on live drum breaks or drum loops onto your samples as the foundation of your drums. You can chop them and arrange them how you like, then throw on your own drums on top of those. It makes the best sound more complete.
In FL if you want your audio clips to stay in sync with any Bpm you use. Click on it and on "time mul" select auto detect, then click on project (at the bottom). This will keep your audio clips in sync.