Place the chicken breasts in the bottom of a 5-quart or larger slow cooker. Add the black beans, salsa, corn, garlic, chili powder, cumin, oregano, pepper and water.
Briefly stir to distribute the spices. Secure the lid on your slow cooker and cook on low for 8 hours or high for 4 hours.
Once fully cooked, remove the lid of the slow cooker. Stir with a fork to shred the chicken; it should shred easily.
To build the bowls, place 1 cup of rice in the bottom of a bowl and top with 1 cup of the shredded chicken mixture. Add a sprinkle of cheese and green onions and enjoy!