Here these two Irish blokes are building a stone round house, inspired by iron age Celtic houses. I dunno if I would recommend their channel, not just because I haven't seen their other videos beside a couple from the house building ones, but I just don't like their attitude, or how they behave.
Notable is the way they haul the rocks to the site, they use a mule to draw a sledge.
https://www.youtube.com/c/SmoothGefixt/videos

This is the cross section of their wall. They dug a ditch deep enough to reach the compact clay layer which undisturbed and solid for the foundation to lay on. But they didn't dug it as wide as the wall itself, but in this narrowing fashion, by the end the ditch is only wide as a spade basically. According to them, it's enough, I think they got the info from someone else.
Then, they filled the ditch with rocks of various sizes. As they reached the wider part of the ditch they started to use larger boulders. After they were well above ground level they built two rings, on the in- and outside and filled the gap between with smaller stones. Up above them they placed through stones, wide somewhat more flat slabs, which can reach through the full width of the wall, solidifying the layer below.
I haven't checked the latest video of this yet.