No pattern...used the zippers I recycled as my measuring stick:)I believe they are 4" for each square...I marked a few lines to make sure I stayed straight with the selvages.
Made a lining that was already sitting in the bags when I slid the zipper side in between the lining and the outside selvage...then pinned in place and sew-sew-sew!! Once one side was sewn...I pinned the other side..then finished. That was it...I have no idea the proper way of sewing a zipper...for I was in wood/plastic shop class when everyone else was in sewing!:)But, I can tell you it is easy and quick doing it that way...right or not;)Hope that helps...Skeat