Place the wrong sides of the fabric together, with the edges matching. Sew with a straight stitch 1/4in (6mm) from the edge.
Press the seam open and trim the raw edges to approximately half.
Fold the seam the opposite way, so that the right sides are now facing and the seam is pressed out to the edge.
Complete the seam with a final row of stitching 1⁄4in (6mm) from the edge. This will enclose all the raw edges.