Slow Cooker Black Bean and Corn Enchilada Casserole

"My aunt made the best enchiladas, ever. They were super simple in that the filling only had two main ingredients, cheese and green olives, but they were always demanded for potlucks and other family gatherings. I adapted her version to a slow cooker and added black beans for a little protein and corn to add a little sweetness. This layered casserole isn't soupy so it's easier to serve, but you can add additional sauce to your liking...."