Hmmm I thought I understood your question at first, and was going to suggest this tutorial as a fun, easy way to use 6 inch blocks (the video is for charms, but you could easily substitute 6" squares).
https://www.youtube.com/watch?v=Uyd3jbTXRS0&t=1s
But now it occurrs to me that maybe I didn't understand your question after all? Are you looking for help with getting the correct size blocks?