Seems like St. Roy has a video of squaring a log with an ax. Layout your cuts
with a chalk line, cut notches every foot or so down to the layout lines, and
split off the intervening chunks. Roll a quarter turn and repeat.

Here’s Roy’s TED talk on the subject -

https://m.youtube.com/watch?v=Au1TbIyLcPU

And another on hewing -

https://www.outdoorrevival.com/instant-articles/survival-shelter-squaring-beams-
by-hand.html/amp