My favorite (and I had to make 780 recently for a quilt) is Lynn Wilder's method for making 8 at a time. One light square and one dark square. Size of square is size of finished HST (which from your measurement is 2") + 1" X 2. In your case start with 2 6" squares. Sew and cut and trim and you have perfect square that join precisely. I have trouble copying the link on my IPad to how to cut and my hint for using blue painters tape but if you click on my name and go to my recent started threads, you will find it. Easy method