Bat and scorpion carcasses are useless until you build a cooking table. It costs 2 wood planks and 1 leather, and once it's at camp it turns carcasses into drumsticks and scorpion tails and cuts raw meat into steaks.
How do you get the cooking bench in Deep Dish Dungeon?
Craft it at camp from 2 wood planks and 1 leather. The recipe shows up in the crafting menu after you've built the crafting table.

If leather is what's holding you up, see how to get leather.
Once it's placed, walk up to it and press E on the COOKING TABLE prompt to open its recipes.

A stew pot or cooking pot won't process carcasses. Only the cooking table does.
What do you do with a Deep Dish Dungeon carcass?
Keep them. Carcasses don't seem to spoil, so store them in a chest until the cooking table is built, then process them there.
| What you have | What you get at the cooking table |
|---|---|
| Bat carcass | Raw drumsticks |
| Scorpion carcass | Scorpion tails |
| One raw meat | Three raw steaks |

A whole bat carcass can't go on the rotisserie. Turn it into drumsticks at the cooking table first.
Rats are different: they break down into raw meat and animal hide without the cooking table, and the hide is what you need for leather.
How do you turn raw meat into raw steaks?
Pick Raw Steak at the cooking table. One raw meat makes three raw steaks, which you can grill on the rotisserie over the campfire or use in other dishes.

How do you light the cooking pot?
Build a fire next to the pot. The cooking pot needs a fire beside it, not underneath it, and you can't move the pot once it's placed, so pick the spot before you build.
The pot itself is crafted from 1 iron pot and 3 iron rods. It's the station for broths and stews.

Iron rods are scarce early on and the workbench needs 2 of them, so check how to get iron rods before you commit them.