I made one a few months ago for Project Linus from a Veggie Tales book. The cover and back page were bigger than the other pages, but I just bordered out all of the blocks each in a different color, and it went together nicely. Bordering works for me, because I am always struggling with the way things are printed on panels (off grain and not standard sizes). Once you have it bordered, you can trim to accurate size.
Dayle