Base slab for passive house tender text

Hello, I have purchased a passive house kit in timber frame construction. Now I want to commission the floor slab. Level ground, approx. 60cm humus, below that clay. Size of the slab approx. 60m², approx. 20cm thick on glass gravel, with 80mm rigid foam as lost formwork. How should the tender text including earthworks be worded?

Best to first commission a geotechnical report, and then tender according to the recommendation given there?

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