I'm building a deck over a walkout basement. I want to put a concrete patio below. Can I dig the footers (3 total) to depth of 30" below the frost line and then do a monolithic pore of the concrete for footers and slab? I plan to use simpson post base over the footer location imbedded in the concrete. The other option is to use the concrete tubes and do the footers/concrete piers first and then poor the slab around, but trying to save time.