Discovered it very late, here still in case someone else is looking. What worked well for us: We sowed green manure, which we only had to plow under afterwards. The topsoil that had been removed before I sowed with a flower meadow, of course we had to mow it before sowing. The next year many poppies ventured through the lawn, most of the flower meadows are actually annuals. They are good insect pastures. We also worked a lot of compost into the beds. The compost that had been heated produced clean beds. The unheated one created weeding work in the first half year, after that everything was okay.
Glad that your house is finished, Evolith! Are you satisfied?
Best regards Gabriele