Purchase a length of belting and two D-rings. I took my waist measurement and added a 1/2 yard to determine the length of belting I wanted. My belting was one inch in width and the D-rings were 1 inch rings.
Thread one end of the belting through the D-rings and pull through about an inch-and-a-half of belting.
Stitch the belting to itself as close to the D-rings as possible. I stiched up and down and few times for reinforcement.
Put on your belt and determine your finished length. Cut the belting. Fold the unfinished end under itself and box stitch to finish.
That's all there is to it. For a fun look you could stitch ribbon or fabric onto the belting. The possibilities are endless.