Turn the fabric tube right side out. The easiest way to do this is to pin a safety pin to one end of the tube and feed it through the tube and out the other end.
Center the seem so it is in the middle of the fabric and press flat. Topstitch along each long edge, about a 1/4-inch from the edge. If you like, you can also top stitch a few lines down the center.
Next Step: Sewing the Sides
