When the scraps get down small, I cut them to 2 1/4 wide (I know, my first one was that measurement instead of 2 1/2) it doesn't matter how long they are..........long or short.........as long as they are the width of 2 1/4 I place them in a container by themselves.
once I get a few and I want to mindlessly sew, I sew them end to end (I don't mess with diagonal- I just sew them) then I roll them up into a roll.
when I get a huge roll, I will unroll it and sew the ends together jelly roll race style and cut . repeat until the whole thing is done. You could get to a size you want and then just add to the sides as you go along after it is a certain size.
an easy way to get a quilt top of scraps........maybe even a donation quilt............or if you pick certain colors you could make a controlled scrappy........possibilities are endless.........I have a small little roll started from all the sewing I have been up to. I have a lot of small pieces and need to get some lengths to mix in.