I looked at the website, and it leaves out one step that I think is very important. I put a 1/2" fold before I sew the sleeve down. If you just fold your tube in half and sew it down, there will be a bump in front where the rod goes through the sleeve. By making the 1/2" fold, you give the sleeve room for the rod so the front of the quilt will hang flat.
Here's the method I was taught.
I use the same cutting directions: 9" wide x the length of the quilt minus 1", fold each end 1/4", then fold again and sew. Of course, if your binding is wider than 1/2", you would have to make your sleeve shorter. Then fold the fabric in half, wrong sides together and baste tube at 1/4" to make a 4-1/2" wide tube. Fold the tube 2 inches from the basting and machine baste 1/2" from fold. Mark the center of the back of quilt and the center of the tube, then pin from the center to each end, raw edges together. Be sure the 1/2" fold is on top and sew a 1/4" seam. I do this, because I found that 2 layers of the tube, backing, batting, top, and 2 layers of binding were a little awkward and fabric tended to slip. If you don't have this problem, you can leave out this step. Press the sleeve flat. Now, add your binding as you usually would to the front of the quilt, then hand or machine sew the binding down. Tack down the bottom edge of each side of the sleeve and tack down the bottom of the sleeve. Remove the basting from the 1/2" fold.
It isn't as complicated as it sounds. Just take it step-by-step and you will be pleased with the results when you hang it up.