Yes. You can actually boil water in a hole in the ground, and I’ve been trying it in different ways for years.
Through trial and error, I’ve finally found the secret: dig your hole in clay soil. Now I’ve rock boiled in plenty of holes in the dirt, when no other vessel was available or a lack of time prevented my construction of a container. The method is a last ditch effort (no pun intended), to get water that has been boiled to kill pathogens. It always starts out fine, but then boiling bubbles created by the red-hot rocks quickly turn the puddle of muddy water into a puddle of hot mud.