You can if you VERY carefully fold each block in half and then half again, press the block to help hold it folded. Then take your 9 1/2 inch square ruler, lay it so the 7 3/4 inch line is on the folded edges and trim. When you unfold the block it should measure 15 1/2 inches square. You may want to try this out on a scrap before you actually cut one of your "good" blocks.