Personally, after the onslaught, over the past decade of Flea wannabes completely playing out the whole notion of slapping, and doing it so poorly, without any semblance of feel or nuance, I could do well never to hear any slapping again.
When done soulfully, where you don't hear a barrage of bippitty bippitty boing boing for 5 minutes, yeah, I can relate, but beyond that, I'll pass entirely.
What's sad is alot of novice players start slapping WAAAAAAY before they have any right to.
Learn your fingerboard. Learn how to play a pocket with feeling. Develop a modicum of technique. Spend a few years playing with good drummers and get inside their heads.
THEN work in the thumb.