I cut scraps and "unwanted fabric" into sizes I use on a regular basis. 2.5" strips, 5" squares, 3.5" strips are the ones I cut the most of. The strips can always be cut in squares or rectangles. And then as I go, I cut the leader/ender project size I am using. Still working on Bonnie Hunter's Tumbler LE from 2015 and have another ongoing LE that is still not large enough. I also use shorter scraps to cut for piano borders (scrappy is great) and also use "one of a kind" strips in making ahead scrappy binding bundles. I call this my mindless sewing times.