Wash the newly bought casserole with detergent, pour in a small amount of uncooked rice, add water and a few drops of peanut oil, bring to a boil with low fire, keep stirring to avoid burning, turn off the fire for one hour, let stand overnight, pour out the porridge, clean it with detergent, wipe off the water and air dry naturally. Then pour in rice washing water and soak it for one day, so that the clay pot can absorb enough rice washing water, and the starch in the rice washing water can fill the gap in the casserole. Then clean it, dry the water, and air dry naturally, so that the clay pot can be boiled.