To make chicken stock: Within a day or two, remove the lemon slices, then add the carcass to a pot of fresh water. Simmer the carcass with any remaining broth and vegetables from the pan on low for two or three hours. Check that the water hasn’t gotten too low, and add more if the bird looks dry. It should mostly be immersed. Once the bones have become very soft, remove from the heat. Add a large bowl to the sink basin, place a fine-mesh strainer over the bowl, then pour the pot’s contents over the strainer and bowl so that the bones, skin and meat are left behind in the strainer. Discard. Let stock cool, then transfer to clean containers. Use or freeze within two days.