Now that the binding is finished, the bottom band can be sewn on and we will have our Yellow Polka Dot Bikini ready for the Grand Finale! Cut a strip of fabric at least 10″ (25 cm) longer than the total width of the two cups. We are going to use elastic across the bottom, so the width of the strips should be two times the elastic width, plus two seam allowances. It can be cut wider now and trimmed later if you aren’t sure of the width.
Press the strip in half lengthwise to mark the centre line, or mark the centre line with a wash-out marker. Position the elastic (I used bra strap elastic, but almost any elastic will do) along the centre line and stitch it down with a wide three-step zig-zag. This will hold the elastic securely yet still allow the elastic to stretch .