Place chicken breasts in the slow cooker. Add the enchilada sauce on top of the chicken, then top with the taco seasoning.
Cook on low for 2 hours. Check chicken to ensure it's done.
Remove the chicken from the slow cooker. Shred with a fork. Return the chicken to the slow cooker, stir, and reduce the slow cooker to warm.
If you need to cook the rice, do so now. Preheat the oven to 350°.
Coat a baking dish with nonstick cooking spray.
Assemble each enchilada: Place rice, some shredded cheddar cheese, and chicken into each tortilla. Roll and place in the baking dish. Top the enchiladas with more shredded cheddar cheese and some salsa.
Bake for about 20 minutes, or until cheese is melted.
Serve and top with sour cream if desired.
You can use frozen chicken breasts for this recipe. Still check them at 2 hours for doneness.