There is no right or wrong way to shape the handle as long as it is fitted very tight in the metal part. It may depend on what tools you have. I turned the small and round end in a lathe so that is was close then finished shaping with a hoof rasp. I started with it longer then needed so I had a piece to chuck on the lathe and cut off the excess after I was done in the lathe. The part I cut off is still in the lathe.

The metal part that the handle fits into is cast and not machined to a perfect circle, mine was out of round 20 or 30 thousands. That out of roundness helps to keep the handle from turning but is does require actuate and very tight fitting. The finish surface of the handle is not sanded supper smooth and left a little rough for a better grip.

You have to start with a bone dry piece of wood and/or treat the wood with something so it will not dry out or shrink in use, I did both. What may be tight in damp humid weather conditions will most likely be loose in dry weather conditions.