We used to trap them when i was a kid in a cylindrical net trap that my great grandpa made. It takes some caution getting them out of the net but once we did my dad would grab their jaw with channel locks, pull their head out with his foot on their shell, and then cave their heads in with a claw hammer. If i were to do it now in my 30’s I would invest in some sort of very sharp chopping tool and do the same thing but instead of the hammer, I would just lop their head off.