to put in detail what he said
Fl slicer:
Dis what I do..... take a part of of a song I want den I mark the song on every kick and snare(in sony acid by looking at waves)...
when you importing in to fl slicer ur sample may be strecth already if you speed it up in another program.
den I put it in Fl slicer (While I was in acid I speed tha sample up or slowed it down by adjusting bpms) den I match the bpm to the tempo.
Next you dump it in the piano roll but the catch is you gotta delete it and re compose tha song to where a kick(or snare) will be on the Fl grid once you do dat with each chop you select the "A" function(mirror) and what dis does it puts an echo on tha beat you move the slider up or down to it plays perfect and when it does you drum pattern should be on point....Really useful for samples dat have kicks dat are off(no fun intended lol) or when you trying to layer perfect.... learned it tha other day...I ju been working with the loops for bout 5-6 months

I got a vid let me see if I can find it