Start by cutting a strip of fabric about 19 inches long by 5 inches wide.
Fold in half, right side together and sew in the length, leaving the ends open. Turn inside out.
Cut a piece of elastic roughly the same size of the strip and insert from the one end and pin onto the other end. Sew.
Bunch the fabric up till you are satisfied with the amount of "scrunch".
When you're happy with your scrunches, sew the end of elastic in place and cut the extra piece off.
Fold ends together, pin, stitch and trim close to the stitch line.
Turn the stitched edge to the inside, ruffle your scrunches along till you're happy with the look and you're done :)