Terracotta pots, like ceramic ones, retain heat and slowly release it. This means that the heat will stay inside the grill instead of radiating away from it through the terracotta material. When choosing terracotta, use only unglazed pots or planters at least 1 foot deep and 1 foot wide. Glazing can create noxious fumes or byproducts that could taint your food.
Building a terracotta grill for high-heat cooking, like searing steaks or cooking hamburgers, requires a different design than a grill built for slow-smoking. Choose a deep, unglazed flowerpot and fill it with sand or dirt. While you will not use the pot for planting, the sand is necessary to keep the heat from the fire from damaging the pot. Leave 6 inches of space below the top of the pot free for the charcoal and grill cover. Cover the sand with a large sheet of heavy-duty aluminum foil so the grease dripping down and ashes from the coals will be easier to cleanup. Pile charcoals over the foil and place a spare oven grate on top of the pot.
A slow-smoking terracotta grill is best for thick foods like chicken or vegetables that require more cooking time to ensure the inside is done. Terracotta smokers use an electric hot plate or a very low-heat fire in the bottom to heat a bowl of soaked and drained hardwood chips. If using a low-heat charcoal fire in the base of the pot, line the bottom with a layer of sand and place foil on top of the sand to protect the pot. Place the smoking chips directly on top of the charcoals. The food rests on a grate at the top of the pot. A second terracotta pot placed upside down over the smoker creates a lid to trap heat and smoke. For this grill set-up, you will need a grill thermometer to monitor the temperature to ensure that it does not dip below 250 degrees Fahrenheit. Temperatures that are too low can lengthen the time the food is within the danger zone temperature range where bacteria can multiply. For best results, set the smoker so it maintains a temperature of at least 300 degrees Fahrenheit.
Using a Homemade Terracotta Grill
Use a terracotta grill built for high heat as you would use a barbecue pit with charcoals. Light the coals and wait for them to burn down to embers before beginning cooking. With a smoker set-up on your grill, cook thick foods between 300 and 350 degrees Fahrenheit until cooked through. Proper use of a food thermometer will ensure that no matter what you cook it will be thoroughly cooked to a safe internal temperature.