The final step is the waistband. Since I had problems sewing the side seams together due to the thickness of the elastic, I chose to sew the waistband in the round, after stitching the side seams.

Cut the elastic to the desired length and sew the ends together to make a circle. Be careful not to twist the elastic. You can join the elastic several ways. For this pair, I butted the ends together and used a wide, short zig-zag stitch to sew them together.

Divide the elastic circle into fourths and mark each position on the elastic. Mark the waist of the panties in the same manner.

Align the marks on the elastic with the marks on the panties, placing the elastic on the outside of the panties, tops aligned.

Serge or zig-zag along the top edge, stretching the elastic to fit the waist of the panties. Be sure to stretch evenly and don't serge over any pins. Go slowly.

Flip the elastic up so that the seam is on the inside.

Topstitch the waistband to make the seam lie flat. You can use a zig-zag or a twin-needle stitch. I used a twin-needle stitch for this pair, but a zig-zag looks nice, too. Trim threads and you're done!

Here are two pairs finished. The top pair is made from the same pattern and fabric with stretch lace at the waist and leg openings. The stretch lace worked great applied flat as described above. If you choose to do it this way, be sure to finish the ends of the serged seams neatly.

This pair is from the Kwik Sew Lingerie book. You can't really tell from the pictures, but this pair is more loose-fitting than the others. I like the fit of the front of this pattern and the back of the swimwear pattern. Hmm...can I put them together???