Originally Posted by tallchick

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.

Originally Posted by QuiltBaer

Lay one 3 1/2" square on the rectangle and sew on the diagonal. Trim the excess away and press the triangle to the outside corner. Lay the remaining 3 1/2" square right sides together on the opposite end of the rectangle. The second square will overlap the first seam and that is correct. Sew on the diagonal. Trim the excess fabric to 1/4" and press.
That is just one way to make Flying Geese.
Hope this helps.