If you find that your pockets are gaping after sewing them in, skip the optional topstitching step, and sew the pockets down to the lower front panel of the dress.
With your dress inside out, fold the pocket over until it is facing the dress. Carefully pin the pocket to the lower front panel. Stitch around the perimeter of the pocket at 1/4" (2cm) to secure. Repeat on the other pocket.
Press stitching on right side.