Is there some formula, or how do you know how large to cut quilt pieces so to get the corner points to be right. In the past, my Mom would draw her design on paper, cut out the pieces and then redraw on cardboard with the 1/4 inch seam added. I bought plastic quilt squares, 12 1/2", 8 1/2", 6 1/2" and 4 1/2" but do not know how to use them to make the pieces come out right. My center square is the 61/2". How do I make a triangle to sew onto the edges and have points when my next piece goes on? Thank you so much for any advice. I have struggled with this all day and all my squares do not have points. Thank you with hugs, Barba