Add half a bowl of water to the bowl, stew it in water, stir it with chopsticks from time to time and melt it. You can also add red dates, rock sugar and so on. According to your taste or efficacy. I often do this. It's delicious.

Any bowl will do. It doesn't need to be sealed. Just add some water and steam it in a pot until it is completely melted.

You don't have to stamp it.