To use a leather belt for purse or tote bag handles, first assemble the tools. My favorite sources for belts are the Goodwill where they are $1.99 each, or the Genesis Thrift Shop in Dallas where they cost less than $5. I've tried lots of different kinds, and I prefer leather that is not bonded or sewn. Lots of belts are a different color on the back side. For handles I like the front and back to be the same color.
Cut the leather to length. If you don't like the holes in most belts, cut the the end off and make a shorter strap. Or punch holes the entire length of the belt to make them look intentional.
The easiest way to attach them is to use rawhide and lace it in place. The rawhide lacing makes a nice, strong junction. I would hate to have the handles fall off of something I had made.
For a rawhide lacing attachment, use a leather punch for a nice neat hole. Depending on the size of the bag, I usually either use four holes or six, but you really could lace it any way you would like. On the natural colored wool bag in the photos there are four holes in each end of the belt. Since the top of the bag is folded over, I put a slit in the top edge and sandwiched the leather in between the wool so the lacing could go through two layers of felt. It is a fairly large bag and I wanted it to have extra load bearing area. I use small scissors that have a very sharp point for poking holes in the felt. You can see the belt end peeking out of the bottom of the folded over edge in one photo.
If you don't want the lacing to show, cover it with something. On the outside of the bag I sometimes use beads threaded through the lacing. On the inside I often line the top several inches to both cover the attachment and add a contrasting color or texture.
When using belts that are woven strips of leather I poke the lacing through existing gaps instead of using a leather punch.