Slow Cooker Chipotle Chicken Fajita Soup

Name: Slow Cooker Chipotle Chicken Fajita Soup
Ingredients: 1 pound boneless skinless chicken breasts (about 2-3 breasts); 2 teaspoons ground cumin; salt and freshly ground black pepper; 1 onion , chopped; 14.5 ounce can diced tomatoes with green chilies; 1 chipotle chili in adobo sauce PLUS 1 TBSP sauce from the can*; 1/2 teaspoon dried oregano leaves; 1 cup frozen corn; 15 ounce can black beans , drained and rinsed; 1 bell pepper , chopped; 2 cups low-sodium chicken broth; 1 avocado , for topping; 1/2 cup fresh cilantro for topping; white corn tortillas for serving