Drilling foundation for greenhouse?

A greenhouse is planned. Because I do not want to work with acrylic glass, I have to provide a foundation that does not shatter the glass. Since the garden is on a slope, it is difficult to get even small excavators there. Therefore, I am considering making holes with an earth auger (12 to 15 centimeters in circumference, 80 deep), filling them with reinforcement and concrete, and placing the individual posts on top. The diameter of the basically round "house" is planned to be 3 meters. I imagine that "around the circle" maybe 8 posts will stand, and the slope will be excavated at the top and filled up at the bottom, supported by stone walls (without deep foundations). Presumably, such slender columns – also deep enough – are relatively easy to drill and don’t require much concrete. I have two questions "to the group": 1. Does anyone know such earth augers and have already used one? I would prefer an electric auger because motors are too loud and prone to failure for me. They are often praised on the internet: "this works great," but of course anyone can write anything... :rolleyes: 2. How do you assess this: A row of posts on which a welded steel structure is placed. Will this hold? Or will the posts move over the years so much that it rattles? Of course, it depends on the soil. I have known the site for 4 years now, and it seems quite stable to me. In terms of weight, I estimate that it will weigh "something" (steel and glass), but it will not be a "heavyweight."