One large square is 6" +1 1/4"= 7 1/4' The smaller square is 3"+7/8"= 3 7/8". After following the rest of the directions and making 4 squares you should have a 12" block finished. She shows about 2 1/2-3 minutes in how to attach the smaller squares to the larger squares. Make sure they're aligned on the diagonal correctly. I'm working on a border for my son's quilt. This is the easiest pattern. Just add 1 1/4 to the large size square and 7/8 to the smaller.