8. To make the side seams, place a wooden ruler or straight edge about 5/8 inch in from the edges. The wooden edge will ensure that the heat of the iron melts only the side seams together and doesn’t fuse too much of the bag front to the back. Make sure the top flap of the bag is open and doesn’t get ironed into the seam. Protect iron and board with parchment, and iron the seams together on both sides until they’re completely fused. Take special care to iron the sides of the pleat as there are several layers of plastic to fuse.