Add chicken, corn, black beans, onion, bell peppers, garlic, chili powder, cumin, paprika, salt, black pepper, red pepper flakes, and chicken broth to the slow cooker.
Cook on high for 4 hours or on low for 8 hours.
Remove chicken and shred it with forks; set aside.
Gradually add freshly shredded cheddar cheese to the warm soup, stirring until melted and combined.
Whisk together flour and heavy cream until smooth, then stir into the soup.
Return shredded chicken to the slow cooker, cover, and cook an additional 30 to 40 minutes.
Serve the soup warm topped with chives or green onions, avocado slices, tortilla strips, and extra ground black pepper if desired.