I make mine in a similar way, but I start with a square, cut it into 2 triangles, stitch it into a bias parallelogram then proceed as instructed here. I get about 5 yards of double fold bias tape from a fat quarter of fabric with a 4" x 18"piece left over from making my initial square. I also do it with other size squares of fabric. You'll find similar instructions for cutting continuous bias binding in may current quilt publications.