Prefabricated house construction - who creates the plan for the earthworks?

You already have the plot? With a slope. Sounds interesting. The forum often helps with clarifying where the house should be placed. Don’t you have any idea how it should look?

Of course we already have ideas about that. I acquired the plot and, as mentioned, it is only very slightly inclined.
But your answers to the original question have already helped me a lot.
Thank you :)