You can flour a tea towel and proof it in a colander. It gives you a nice shape.

I don't find my pot needs a preheat so it just proofs in the pot. I use an Emile Henry potato pot (glazed clay) but I did the same with a Lodge dutch oven (cast iron)

I bulk ferment in a metal bowl or cambro tub. Then I shape after doing a bench rest. After shaping, the dough goes into a banneton basket for the proof. Using a banneton allows me to preheat my oven with the Dutch oven inside to get ready for baking.

I use a medium sized mixing bowl or sometimes my KitchenAid mixer bowl, which is relatively narrow at the bottom so it doesn't spread too much.

I don't use the baking pan because I use cast iron and I worry it would rust

I put it onto parchment and back into the bowl of the first proof after cleaning it out.

… where do you let it sit for the second proofing? I’d think to do it in the bread pan where I’ll bake it, so it assumes the shape of the final loaf. But then I always put the dough into that pan once it has been pre-heated in the oven. Do I let it proof there, take it out, pre-heat, then reinsert?

Am I missing something obvious? For what it’s worth, I use a ceramic, lidded loaf pan baker.