IIUC the easiest way to boil stuff without ceramics is usually in an animal's stomach or intestines. I believe you can also do it in a lined wicker basket.
I'm not sure exactly how these things are done but both of them seem much easier to figure out than how to fire a pot! (Requires very high temperature and a good understanding of the material to stop it cracking)
You have to invent a whole lot more to have a plastic bottle or even a paper drinking cup, at that point, it'd be simpler to just invent pottery, instead.
I'm not sure exactly how these things are done but both of them seem much easier to figure out than how to fire a pot! (Requires very high temperature and a good understanding of the material to stop it cracking)