Measure the waist and cut the elastic to the desired length
Overlap the elastic ends and sew them together securely
Divide the waistband and elastic into equal sections and mark them
Pin the elastic to the inside of the waistband at the marked points
Stretch the elastic evenly as you sew it to the waistband
Use a zigzag stitch or stretch stitch to attach the elastic
Sew around the waistband, keeping the elastic evenly distributed
Backstitch at the start and end to secure the seam
Fold the waistband over the elastic if needed and pin in place
Sew the waistband closed, leaving a small opening if required
Press the waistband flat and check that the elastic moves comfortably