Welcome. Another factor that we don't know is the size of the hexies you need to cut. If they are small you might be able to get more than one row on your fabric because by drawing them onto a grid you would not have any waste because they would butt up against each other. If you cannot butt them together you would have lots of wasted fabric or scraps. I would recommend, as others have, that you draw it out. You can buy lots of cheap paper in rolls to draw on-I just discovered the rolls of paper at Lowe's or Home Depot that they use to mask windows when they are going to spray paint the exterior of a house.