Step one: Fold down about 3/4 inch at the top and bottom ends to create the pocket for the drawstring. Stitch straight across at both ends.
Step two: Fold fabric in half with wrong sides on the outside and right sides together.
Step three: Stitch along sides of bag, stopping at the stitching line for the drawstring pocket and allowing about a 1/2 inch seam allowance.
Step four: Turn the bag right side out. Using a 10 inch piece of matching rat tail cord, thread the cord through one side of the pocket, turn and come back through the other side. Knot the ends of the cord.