My process with random scraps is to just begin sewing pieces together. When one piece runs out, I just put another one on and in this way, will end up with a lot of different fabric pairs in a wide range of sizes. I iron these strip sets open and then proceed to sew pairs together, often turning to sew a strip set across the end or another, but I change it up as often as possible so I end up with a lot of different configurations. Below - I have a lot of rectangular shaped parts spread out on the ironing table. These, will now be matched up for size and when I find two that fit together somehow, I will stitch again.
The best thing about this process - why I like working this way is I never know what I will end up with - the element of surprise is very motivating!