Just cut away! You'll have to straighten up the edges when the quilt top is done no matter how carefully you tried to cut the ends. It won't matter if they are straight or not. I've made three of these so far, two large ones made with 40 self-cut strips (no jelly rolls to use, just yardage to cut) and one baby quilt using 20 strips. Don't expect it to go as fast as in the video! I think it took me at least 3 hours to sew each of the large ones. Good luck with yours!