What you need:
Skirt (a size or two too big)
Step 1: Big Skirt
First, you need a skirt that is about a size or two too big. Turn it inside out, and lay it flat.
Then, measure about two and a half inches down from the top of the skirt, and pin.
Step 2: Elastic
Using the elastic, measure your natural waist, and cut the elastic. It should be snug but not too tight.
Next, pin the elastic along the skirt where you measured.
Step 3: Sew That Thing!
When sewing, make sure that you hold the fabric taut and flat when going through the machine. And, believe it or not, thats it!