Use the container to trace the top and sides of the container against the fabric.

Line up the edges of each side to the corresponding edge and sew in place for three of the edges. For the fourth edge, extend where the line should be sewn by ½ of an inch.

Fold over the long edge that would line the side of the container. Sew a tube large enough to house the elastic band. With a 1-to-2-inch opening on one side.

Pull the elastic band through the tube to make the elastic shorter than the tube itself. Sew the end together and pull the elastic fully into the tube. Close the opening in the tube. Trim excess fabric as necessary.