I make those, let's see if I can explain. I cut a strip 1.5" wide and about 5.5" long. Fold in half long ways, right sides together, and sew a 1/4" seam. Turn right sides out. I wiggle it with my finger until the seam is down the middle of one side and iron it flat. Fold in half and mark the middle with a pin. Unfold and lay flat. Hold the pin and fold each side on a diagonal to form the triangle at the center. Iron flat and then sew across the fold to hold it in place. I hope this helps.