I did not cut my original strips to the correct 37 and 39 inches. I cut the pieces from selvage to selvage then sewed those together. This left me enough length to square up the edge when I cut the selvages off. I only have a 18 by 24 cutting pad so I planned ahead for this. I had to iron everything really flat so that I could fold it twice. (4 layers) I squared up my edge and cut the strips. When I had to move the piece to be able to cut more strips I did have to cut another 1/4 off to make it square again. It may have been easier if I was not using slippery polyester.