I see the cement added after the wall erection, but what is the structure for the wall underground pre-concrete? I don’t see that part being installed. Granted it may be a simple ditch with a long pre-fab rectangular frame that was done before the video started.
I watched a video that looks like it's about a 6'-8' deep and about 6' wide trench dug, the fence put in, then concrete poured to secure it.