Washable fabric glue (available at craft stores; we used Fabri-Tac glue)
Clear nail polish
45-inch cotton drawstring
Decide on the length (one way is to measure the length of a skirt your child likes). Add 1 1/2 inches for a casing to that measurement. Use that total to measure from the open edge of the pillowcase (which will be the hem) and use tailor's chalk or a pencil and a yardstick to mark a straight line across the case. Cut along the line. Discard the closed end of the pillowcase. Turn the skirt piece inside out.
Iron (adult supervision recommended) down 1/2 inch along the cut edge.
Along the same edge, iron down an additional 1 inch.
Place cardboard under the pillowcase to protect the ironing board from potential glue spills. Lift the casing and use a small brush to apply washable fabric glue (adult supervision recommended) along the 1/2-inch edge of the casing. (Tip: This is easy if you drape the skirt around the ironing board and rotate it as you go.) Fold the glued edge back down to form the casing. Use your fingers to press it in place. After the glue dries, turn the skirt right side out.
At the center front of the casing, apply a line of clear nail polish (supervise younger kids). Let it dry and reapply.
When the second coat is dry, cut a slit for the drawstring. Be sure to go through just 1 layer of fabric, and stay within the boundaries of the polish.
Attach a safety pin to one end of the drawstring and feed it through the casing. Knot the ends of the drawstring, and the skirt's ready to wear.