Free hand milling is a way to mill logs in to lumber with swinging motion and a chainsaw. The benefit is that you can do this everywhere with just a chainsaw. Proffesionals in Asia and South America are often quite good in this and it gives a fairly straight cut!
This secret is that a fairly straight cut is good enough because after drying it will warp anyway!
What I prefer is too give a log 1 or 2 straight sides and finish the rest on a big tablesaw. Much easier.
One of the bushcraft YouTube channels that I like made a video about it.