Prepare the ingredients by chopping the bell peppers and mincing garlic if desired.
Layer the chicken breasts in the slow cooker; top with diced tomatoes, black beans, corn, and bell peppers.
Sprinkle cumin and chili powder over the layers; pour in chicken broth until all ingredients are submerged.
Cover and cook on low for 6 hours or high for 3 hours.
Once cooked, shred the chicken with two forks and return it to the soup.
Serve in bowls and garnish with tortilla strips, avocado slices, cilantro, or lime juice.