Depends on how small the piece is before it becomes a "scrap"
I prefer to NOT cut up the larger pieces ahead of time - because if I trimmed it to 2.5, what I now need is 3.0.
I DID trim the 'Swiss Cheese' left over from the I Spy squares I fussy cut, into 2x5, 2.5x5, and 3x5 pieces and those are stored in a small plastic drawer thing.