I just realized that my cutting directions are incorrect for the color book tutorial. Sorry about that! Rather than cutting twelve 8.5 by 8.5 inch squares of muslin, you really need to cut ten of those plus two 9×9 inch squares.
This may seem like an inconsequential change but I forgot that for the two cover squares, we’ll be cutting them along the diagonal (to make four triangles), rearranging them and then sewing them back together. When we do that, we lose the seam allowance out of the diagonal line of each square.
Nik helped me do some geometry to determine that if you’ve already cut your squares, you’ll be OK. You’ll just have .15 inches to work with when trimming your squares instead of .65 inches. It’s definitely useful to have a math teacher in the house! 🙂
I fixed the directions in the original post.