Not to be a snark but what else would they have been expected to do?
Take-out
Oven baked
Microwave
???
Doorless Dash... Hey, you weren’t there. ;^)
Boiled food probably antedates hard cookware like ceramic pots — the ingredients including the liquid was suspended in a skin bag.
Ovens, they probably had those, also wrapping food in leaves and such and burying them a little, they building the fire atop it, was the forerunner of the oven. In Polynesia that’s know as an Earth-oven, works for taters and sweet potato, fish, whatever.