I purchased a sheet of template material from JoAnn's (40% coupon) and cut it into 1" squares. I then used a hole punch to put one hole in the middle of each square. I took a Sharpie pen and wrote row/block numbers on each one -- 1-1, 1-2, 1-3, etc. I use a straight pin to pin each square to the upper left corner of the blocks - I store each group of ten on a safety pin so they don't get too mixed up. In a pinch, I have cut paper squares to use in the same way.