What preparations are necessary for creating a floor slab?

Hello everyone, I have the following question: what preparations are necessary for concreting a floor slab? Do the craft businesses take care of these or must this be commissioned elsewhere? So excavation, compaction of the subsoil, possibly gravel subbase, etc.. Thank you very much!

Hello house building blog, this is about a ground slab for a wooden single-family house, 1.5 stories with approximately 10*9 m floor area. The subsoil in the rear part consists of top-quality topsoil covered with grass and hazel bushes, in the front part there is an asphalt layer with gravel substructure. As a treat, there is also a non-drainage wastewater pit in the grassy part with about 2 cubic meters made of concrete rings that has never been used (so it is empty except for a few cm of water). This pit will certainly have to be filled or even removed (?).
Greetings Till