A coal or kerosene fire provides the main heat source for cooking in Indonesia. However, since the weather is hot and fuel is expensive, many dishes are cooked communally, early in the day, and served at room temperature. A wok-like pan is the main cooking vessel for stir-frying, deep-frying and steaming. Foods are also slow-cooked at a low temperature in covered terra-cotta pots. Many satays and other meats are grilled directly over the fire. In the preparation of spice mixtures, Indonesians use a flat mortar stone -- unlike the deep bowls that the Thai use to roll ingredients into a paste or powder.