Fill your ceramic stoneware piece with hot water. Do not add soap to the water, as soap can affect any seasoning on the stoneware.
Wait 20 minutes for the burned food to loosen in the hot water.
Scrub off as much of the burned food as you can with a kitchen brush and rinse the stoneware. If burned food remains, proceed to Step 4.
Mix 1/2 cup of baking soda with 3 tbs. of water to form a paste.
Apply the baking soda paste to the parts of the stoneware that are still covered with burned food. Leave the paste on the burned areas for 20 minutes.
Scrub off the remaining burned food with a kitchen scrub brush.
Rinse the stoneware with clean water and allow it to air dry.