Just spit balling here but why wouldn't you pour the slab and footing at the same time as one pour?
A vapor barrier covered by gravel can be installed while your waiting for the concrete.
With no inside footer form you can tie the rebar for the slab in now and tie everything together in one pour.
Be sure to add PVC for any electrical work that will need to be encased in the slab...
Several reasons . . .
1 - I'm doing this "mostly" by myself . . . so I'm doing as much as I can to cut costs.
. ( will hire someone to do the pad - don't know enough to do it myself )
2 - The inside will need to be dug out and filled with crushed gravel (ABC stone)
3 - Working my best to fit the pieces into my budget . . . a bit a t a time
4 - Still need to get the wire mesh mats that will go in the pad
5 - They will be connected to the rebar in the footers, so it will basically be a monolithic pad ( just not a single pour)
6 - Figured out a way to get the rebar cages "set" in the ground . . . was worried about them moving during the footing pour
Just trying to keep making progress, and keep it affordable
( with the cost of wood, and now the "claimed" cement "shortage" too )
Sheesh . . finally get to building, and prices of everything is through the roof . . .
(pun intended . . . )