Using sweat pants with straight legs, cut off hem, measure (I used 20") mark cutting line.
Step 1: Cut
Cut, fold right sides together, pin
Step 2: Sew
Sew around, leaving an open bit to turn it right side out. I was using a straight stitch machine so I pulled the fabric a bit to allow it to stretch when done, if I had used a zig zag machine I would have used a wide stitch instead.
Step 3: Turn
Turn it right side out through the small opening you left, close the opening, turn the tube until that bit is inside.
Step 4: Wear
Place on head.