I've stated at least 3 times how its poured.
I'm building the way I built under two masons with 45yrs combined from the areas local companies. That is why it is built as it is, with warranty as is by every other company in my area. Retaining walls go deep and to be perfectly honest, nobody in northern VA is putting a 3' deep footer as mentioned around a patio........I promise. I've seen some of those guys work that was 15yrs old, solid and only looked like it needed power washing.
The slab is its spec'd thickness with thicker rolled edges of 8".
Concrete under the fireplace is 10", reinforced.