Cut the chicken into 1-inch cubes. Place the chicken, onion, garlic, cumin, chili powder, oregano, salt and pepper in 3 or 4-quart slow cooker and stir to combine. Add the beans and broth.
Cover and cook on low heat for 8 to 10 hours or on high heat for 4 to 5 hours, or until the chicken is no longer pink in the center.
Stir in 1/2 cup sour cream, corn and 1/3 cup cilantro. Cover and cook on high heat for 20 minutes or until the corn is tender.
Serve with the remaining sour cream, Colby-Jack cheese, remaining cilantro and avocado slices.