A variety of clay roasting or baking pots are used in cultures around the world for preparing foods in gentle, moist heat. Unglazed terra cotta cookers absorb moisture from the food and release it slowly to the outside, slowly concentrating the cooking liquids. Glazed clay cookers trap the steam inside, but allow some to escape from vent holes or deliberately loose-fitting lids. Glazed cookers, such as the German-made Schlemmertopf, are more sanitary, since they don't absorb any juices from the food as it cooks.
Rinse your chicken inside and out under cold running water. Then, pat it dry with clean paper towels.
Squeeze a half-lemon over the chicken, rubbing the juice into its skin. Season the chicken inside and out with salt and pepper, and sprinkle it with the leaves from two sprigs of thyme. Put two more sprigs of thyme into the cavity, along with the squeezed-out lemon half.
Soak the top of the Schlemmertopf in cold water for 10 to 15 minutes. Place the chicken in the Schlemmertopf, and replace the freshly soaked lid.
Place the Schlemmertopf on the middle rack of your cold oven. Turn the oven to 375 degrees F, and close the door.
Roast your chicken in the Schlemmertopf for 90 minutes. Carefully remove the roaster from your oven, and place it on a trivet on the counter. Remove the lid, taking care to avoid the billow of hot steam that will escape.
Remove the chicken from the Schlemmertopf and cover it loosely with aluminum foil. Let the bird rest for 10 to 15 minutes before carving and serving it.
With any clay roaster, it's very important not to allow sudden temperature changes. Don't put your Schlemmertopf into a preheated oven, especially if it's got a cold bird inside. When you take your roaster from the oven, set it on a trivet or cooling rack, not on a cold counter. Never pour hot water in a cold Schlemmertopf, or cold water into a hot one. Any of these errors can cause your roaster to crack.
Soak both halves of your Schlemmertopf in water for 30 minutes the first time you use it. After that, soak the top only for 10 to 15 minutes before each use.