Moats are not hard to dig. Leading a troll back to one also isn't hard, just make a bit of noise by hitting things as you lead it along.

Even without the moat, lead it around and through a bunch of trees. That will slow it down. If it knocks one over, even better. You can jump over logs, but trolls have to go the long way around.

I never got the hang of parrying, and didn't really want to practice on something as big as a troll, but I get along fine with my bow anyway.

Not sure why people are recommending high tier armor and weapons. By the time you have those you don't need troll skins anymore.