I have had the Harbor Freight 10x12 here in Finland for seven years now. The side walls are 6’ 6” and I do really recommend it for the height of it. You may not get snow, but here the horizontal reinforcements are essential to prevent the greenhouse from collapsing under snow cover. People who have built lower greenhouses have had trouble since those are hard to reinforce, so that the additional structures are not in the way. I like that I can use the added reinforcement pipes for hanging baskets and tying support strings for tomatoes and cucumbers. I’m 5’ 6”, so I can just reach the pipes, which are at same height as the side walls. Right now most of my tomatoes have grown well above the side wall height, so I would be in trouble, if the greenhouse was lower.
Mine is built on concrete blocks, which are buried in the ground and above those there is a base made from pressure treated lumber instead of the steel base. The original steel base was rusted, when I opened the box, which had been transported over the Atlantic and kept in dry storage for three years.
You can read here about my building project.
I do not really understand how would it work to use this greenhouse structure, so that the walls would sit in 2’ deep hole. To do that I would buy some greenhouse kit with 4' wall height and get the inside height taller by digging a hole and building the underground walls from concrete blocks or bricks and set the greenhouse on top of those.
Sari