Here comes an easy "drawn" tutorial:
You will need two "clips" and a "belt" ring
A strip of fabric twice as wide as the "belt" ring width (a) so that you are sure the strap made out of it will slide through the ring:
First fold the strip in half, right sides together and sew the open end (lengthwise), I usually leave 0,5 cm of seam allowance. Turn it inside out and press.
Then attach one end of the strap to the "belt" ring as so:
Slide in a clip on the strap-let it loose but pay close attention to have the top of the clip facing the same direction as the top of the "belt" ring, and then insert the strap again in the ring as shown on the figure:
Finally attach the second clip at the other end of the strap as so:
And here is how the final product can be used with any cloth of your choice: