Place the chicken carcass or bones into a medium pot with water. Bring the water to a boil and turn down to low heat. Simmer for 1 hour. Remove the chicken and the bones. Skim the top layer of oil from the stock (if you are using pre-made chicken stock, skip this step).
Add the washed rice to the chicken broth, and bring to a boil. Lower the heat to a simmer and leave the lid on halfway to prevent the soup from overflowing. Simmer for about an hour. If the congee is too thin, continue to simmer. Before serving, give the rice a generous whisk to break up any rice bits.
Salt congee to taste and garnish with chicken, cilantro, green onions, and soy sauce.