To make HST take the finished size you want and add 7/8"; example if you want a 9.5" finished HST (if you are using precuts for the rest of the quilt that are 10"), then add 7/8" to 9 & 1/2" = 10 & 3/8" square. To make things easy you could just cut your strips 10.5 X WOF, subcut to 10.5 X 10.5, draw a diagonal line on back of one piece, place two squares right sides together, sew 1/4" away from center diagonal line on both sides, cut apart, and square them up to 10". That makes a humongous Carpenter's Star but hey, why spend all your time cutting when you want to sew.