Cut two fabric pieces. a. One 18 by 4 ¾ inches and one 9 by 1 ¾ inches. b. Cut two 18 by 2 ¾ inches and two 9 by 1 ¾ inches if you want a reversible headband. Cut a piece of elastic, around 6 to 7 inches long. Fold both pieces of fabric lengthwise in half, right sides together. Press along the folded edge. Stitch the long edges together on both fabric pieces using a ⅜-inch seam allowance. Trim the seam allowance on the smaller piece down to ⅛ inches so your headband will be less bulky. Turn both pieces right-side out. Press both headband pieces to make sure you get the stitched seam up to the edge. Tuck the edge on both ends of the longer headband piece in about half an inch and press it inside. Then, set it aside. Attach a safety pin to the end of your elastic and thread it through the shorter piece. Put a pin to hold it in place, then scrunch the fabric down around the elastic and pin the other end. Stitch through all layers of fabric and elastic on both ends to secure the elastic. Tuck one end of your elastic into the opening of the larger headband piece and pin it in place. Pin the other side and make sure that your headband and elastic parts are both flat. Stitch back and forth across the pinned sections a few times to secure it.