Yes, you did read correctly; however the class is on how to make a disappearing 9 patch! I have my directions & visuals ready for that! Then, based on the size of the squares/blocks & the arrangement of the pieces, is there some way to figure out how much backing is needed? I just want to be ready to answer the questions with an answer that will apply to all sizes. I don't care how much stash I create if I overbuy, but some may not want a "stash-builder" answer.