Probably not the answer that will really help, but you can make them any size you want! Is you plan to use all 9 patches or are you alternating them with plain blocks? Do you want lots of patches or just a few? If you want, for example, a 6 inch finished (sewn together) block, cut your strips 2 1/2 inches each. When you sew them together with 1/4" seams, you will have a 6 1/2" strip. Then cut that strip at 6 1/2" squares. When you sew your next blocks together, the visible or 'finished' block will be 6". That's lots of blocks, so you may want to make them larger. But follow the same plan...determine your finished block size, divide by 3 and then add 1/2" to that strip width (1/4" seam on both sides of the strip). Good luck with your project. Quite ambitious but I'm sure you'll enjoy it.