ᐅ Substructure for Garden Shed

Hello.

I am planning to build a garden shed soon. It will be constructed on paving slabs.
What material do you recommend for the substructure? If wood, which type and how should it be treated?
I am thinking of placing roofing felt under the substructure to protect against rising moisture. Or is something else like pads recommended? If so, which ones?

Thanks in advance

Regards
Christian

We received a substructure made of KDI wood from the manufacturer. I assume it is spruce or a similar softwood. It rests on small stacks of about 0.5cm (0.2 inches) made from pieces of roofing felt to create an air gap.

We have rubber pads (rubber granulate) underneath, or partially suspended slightly in the air at the brackets.