Measure the area you want to cover with the rug. One of the best reasons to make your own rug, aside from low cost, is that you can size it to fit any area.
Cut out the top of the rug from upholstery material and the same-sized piece from the backing fabric.
Cut an equal sized piece of batting, if you want a padded feel.
Paint all cut edges with Fray Check.
Lay the batting on a work table, add a layer of fusible web, and put the backing on top. Follow instructions to iron the backing to the batting.
Flip the fused backing/batting over, add another layer of fusible web on top of the batting, and then lay out the upholstery fabric for the top, face up. Iron to fuse. If you are not using batting, fuse the top directly to the backing.
Finish the edges by adding a border. For example, if you want a border that is 3 inches wide, add 3 inches for fold-over and 1 inch for seams. Cut two border pieces the same length as the shorter sides of the rug (if the rug is square, just pick opposite sides) and two pieces the length of the longer sides plus 1 inch.
Iron under 1/2 inch on each long side of all four pieces, then fold in half and iron down the middle to create the edge.
One side at a time, starting with the short sides, snug the layers of the rug inside the binding, and sew on the outside through all layers using a zigzag stitch.
At the corners of the long side bindings, fold the1/2-inch overlap to cover the rough edges, and sew.