I used some thick belt leather ( drive belts for old fashion machinery) scraps, and cut out squares. Then I cut out slots to fit the tang of my knife. I used Elmer's glue- because that is what I had then-- between the discs. At the rear end of the tang, I had tapped the tang to take a 1/4-20 thread, and then threaded a piece of cold roll steel I intended to use as an endcap. I use a wrench to turn the end cap down on the leather after stacking enough leather on the tang so that I could just barely start the end cap on the treads. Holding the blade in a bench vise, I turned the end cap until it hit bottom on the tang. The glue oozed out of every wafer. I let them dry over night, and the next day went to work with rasps, and files, and shaped the handle. The last thing I did was grind the end cap down at an angle to remove enough weight to balance the blade at the guard. I polished both the metal end cap with various grades of emery paper/sand paper, until I had the finish I wanted. The handle has lasted about 45 years now.
Today, there are better glues. You can buy a rubber bases glue from Tandy Leather, for instance, to glue the leather discs together, or use any number of epoxy compounds.
If memory serves me right, I got 12 leather disc on the tang, and use the endcap to crank them down and compress them. Then I added the 13th disc, and did the final compressing.
Actually, cutting the discs out with an exacto knife blade was the real work involved. I had to be careful with such a sharp knife, but I was cutting through thick leather, too, so it took a lot of muscle to get that blade through the leather. Using such a knife involves small muscle groups in your ands, and cramping should be expected. Take your time, and take breaks, to be safe. Don't work when your hands are tired or fatigued. My tang was 1/4" by 5/8" wide, so that is the dimension of the slots I had to cut in all those leather discs. I think the outside dimension of the leather was 1.5 inches square. I rasped and filed the grip to fit my hands, so the handle is " ergodynamic, many years before that word was invented. The sides are flatter than the ends, and the belly on the end where the edge of the blade would begin, is more round than the end on top.
Do treat the leather, and keep it dry so it doesn't mildew, or rot. I used Neatsfoot oil on the handle.