Hello, the ancients put a thick layer of mud on the place where the stove was built on the ship and put a metal plate on it, which can play a role in heat insulation. Metal has strong thermal conductivity, while mud has weak thermal conductivity (even if it becomes dry mud). Slag discharge, etc. Put it on a metal plate or throw it directly into the water. Before the invention of metal, man could not build big ships. Those ships can't go to the ocean. When they are hungry, they can stop at the dock to cook or eat dry food.