In your crockpot, combine salsa, olive oil, chicken both, water, taco seasoning, black beans, onion, and bell pepper.
Nestle the chicken breasts into the mixture. Slow cook on high for 3-4 hours, until chicken falls apart easily.
Shred chicken in the crockpot with two forks. If there is a lot of excess liquid, try to ladle out as much as possible.
Cut the low carb tortillas into 1-2 inch squares. Mix into the casserole, with as much cheese as you want. Top with more cheese and cook for another 30 mins.
Serve with anything else you like- sour cream, rice, avocado, more cheese, etc