Welcome back! When you sew 2 3.5 inch squares together the resulting unit will measure 6.5 inches because the seam allowance results in the loss of 1/2 inch. The part you cut away are Flying Geese units or the legs for the the star, there are several other ways to make flying geese units if your not comfortable with that method. But yes, the method outlined in the instructions you will cut away the excess fabric leaving 1/4 in seam allowance after sewing corner to corner.
Last edited by tallchick; 01-18-2020 at 01:08 PM.