The Korean hot stone bowl in which bibimbap is often served is called a dolsot. A dolsot is a small cooking or serving vessel traditionally made from agalmatolite, a soft stone that retains heat exceptionally well.
When used for dolsot-bibimbap, the bowl is heated before the rice and toppings are added. Sesame oil may be brushed across the bottom, allowing the rice touching the stone to become crisp and golden. This toasted layer is called nurungji, and the sizzling heat can also cook an egg against the bowl’s sides.
Dolsot means “stone pot,” while the related dish name dolsot-bibimbap means bibimbap served in that vessel. Sot alone is a generic word for a pot, and ttukbaegi is a different Korean earthenware bowl commonly used for stews. Onggi refers broadly to traditional earthenware vessels, not specifically this hot stone cookware.