Old tires might be outside MY tolerance. Haha.
My oldest son’s GF has her garden in tires, an old stone fire pit, a half barrel and a couple of big old broken ceramic urn looking pots. All stuff that was left in the backyard of the house they rent.
The people in that last YouTube video I shared put a lot of support structure into theirs. 4x4s and steel posts. I like the sill/seat on top too.
I like @brew_cat ‘s daughter’s idea of filling the bottom with sticks. I have plenty of down and dead wood around, then maybe I’ll fill the gaps with straw and put about a foot of good garden soil on top.