How big do you want you blocks when you cut them. I made one with 4/12" blocks sewed my 9-patch, cut in half vertical and horizonal. The 2nd block was 6 1/4 or should have been. I think.lol. I re-read. If you want your block after the cut to be 12" you would have to use 8 1/2" squares to make your 1st 9-patch.