I've made 5 Scrap quilts. Four were twin size made following instructions in the book, Log Cabin Quilts with Attitude. You can use any size or shape for the center (square, rectangle, etc.). Then add any size strips to build the blocks. They don't have to be rectangles. They can be cut on the diagonal. When the block is larger than the size you want, you cut it into a square, but you angle the square ruler so they've got "attitude". You cut half of them slanted one way & the other half slanted the other way. Very easy since they all end up the perfect size. Put them together alternating the want they're slanted. It's really fun. I used fabric I've had for years. When my daughter & 2 granddaughters saw them they cried & wanted one. There were fabrics from clothes made for all of them.
The 5th one was a full size crazy quilt paper pieced block. I think the pattern was in the same book. I made 113 blocks. Very time consuming. I worked on it off & on for 2 years. I could use some really small pieces in the center part.
Some blocks I color coordinated, but I like the mixed colors & fabrics the best.
On a Fons & Porter Show, Marianne said if you use blue sashing, it's a blue quilt. So if you want to have a certain color, choose that for the sashing.