My Dad had a simple pit when I was a kid.
He stacked blocks under an old Walnut tree in our back yard.
3-4 blocks high then a heavy wire grate across the blocks.
2 more layers of blocks gave room for 1/2 a hog to smoke.
(All night job)
The top was 2 old metal Piggly Wiggly signs that he could slide back and forth for access.
When he smoked there was enough leaks for smoke to escape easily.
The front of his pit had blocks he moved to build a fire and re-supply logs.
The bottom of our pit was dirt, that was scorched and burnt black,
it was baked like adobe clay.
You may have guessed that we were poor folks.
My Dad was a butcher and cook, so we still ate well.