Step 5: The home stretch!
Almost done now, all we need to do is create another flap like we did at the start, but put it on the other side. So once there are four inches done of the full 42 stitch rows, time to start casting off.
When you're about 4 inches on the full width, and the next row puts your first long tail of yarn at your left (like in the picture), start binding off your stitches. Bind off 28 stitches, (and I always have to double check on this) so that you have 14 total stitches, with one being on your right needle and 13 on your left.
Keep going in your knit/perl sequence from here.