Preheat your oven to 350°F (175°C) and grease an 8x9-inch baking dish. This step prevents sticking and makes for easier cleanup.
In a large bowl, mix together the cream of mushroom soup, uncooked rice, water, sliced carrots, and cooked ground beef. Stir well to combine all ingredients evenly.
Transfer the mixture into the greased baking dish, spreading it evenly.
Bake in the preheated oven for 90 minutes. This long cooking time allows the rice to absorb all the flavors and become tender.
After 90 minutes, remove the casserole from the oven and top it with cheese slices. Return it to the oven for an additional 5-10 minutes, or until the cheese is melted and bubbly.
Notes
Feel free to customize this casserole by adding your favorite seasonings or vegetables.