Place the front stitched lining panels to the back stitched lining panel, right sides together, matching up the hem seams. Pin to secure. Using a 1cm seam allowance stitch the front to the back along side seams. Leave to one side.
Gather up the outer hem so that it is the same length as the front outer panel hem. Pin the frilled outer hem panel, on top of the front outer panel. So that they overlap by 2cm. Stitch the frilled hem to the outer skirt panel using the basting stitch as a guide. Repeat with outer back hem panel and back panel.