1. Stitch front, back, and side darts; press them toward the center.
2. Sew the flap right sides together, turn it out, and topstitch along the edge. Stitch the flap onto the front dart, covering it.
3. Sew the back center seam between the zipper slit and vent marks. Insert the zipper.
4. Sew the front center seam to the slit mark. Press seam allowances open.
5. Press the hem allowance to the wrong side and stitch. Press the integrated vent facing (left back panel) to the wrong side along the fold line and stitch to the hem allowance. Narrowly stitch the vertical seam allowance of the vent (right back panel). Topstitch the left back panel at the top of the vent diagonally, catching the vent allowance.
6. Sew the lining seam, baste pleats. Place the lining inside the skirt, wrong sides together, and baste the top edges. Fold the lining at the zipper opening and stitch it to the zipper tape.
7. Place the waistband right sides together with the skirt's top edge and stitch, leaving the right back edge with an extended allowance for fastening. Sew the waistband ends. Fold in the inner waistband edges and topstitch from the right side along the attachment seam. Make a buttonhole on the left end of the waistband and sew a button on the right end.
8. Finish the lining hem with a narrow hem and secure it at the vent.