Remove bits of meat off the carcass and set them aside for later.
Add the carcass, along with skin and other non-eaten bits from the turkey, to a slow cooker. At this point, you can also add in some garlic, veggie scraps or Thanksgiving leftover veggies to add some nutrients and flavor to the stock.
Completely cover the carcass and veggies with water, and cook at low heat overnight.
If you choose to use an Instant Pot or electric pressure cooker instead, use the soup setting of your cooker and increase the time to 120 minutes. Cook and, once finished, allow the pot to depressurize before opening.
An hour or so before lunchtime, begin preparing the veggies for the soup. Peel the carrots and onion, and thinly slice them along with the celery stalks.
Strain the stock from the bones and cooked veggies, and add the strained stock to a medium pot along with the sliced veggies and herbs. You want to have at least 5-6 cups of broth, so add water if needed.
Cook at medium heat until it reaches a boil, and then simmer for a couple of minutes while you measure out the rice.
Add the rice to the boiling stock, and continue to simmer at low to medium heat for around 15-20 minutes, until the rice is fully cooked.
Add in salt and freshly ground pepper to taste.
Remove the soup from the stove and serve immediately!
Nutritional information depends upon the amount of meat and other leftovers added to the soup. The given information assumes stock obtained from the bones along with rice and veggies. Added meat and other added ingredients will need to be figured in to obtain more accurate information.