Rinse the mixed beans thoroughly under cold water, then drain and set aside.

In a skillet, heat olive oil and sauté the chopped onion and minced garlic for 3-4 minutes until translucent.

Transfer the rinsed beans, sautéed onions, garlic, chopped carrots, diced celery, diced tomatoes, and vegetable broth into the slow cooker. Add cumin, chili powder, bay leaves, salt, and pepper. Stir to combine.

Cover the slow cooker and set it to cook on low for 6-8 hours or high for 3-4 hours.

Once cooking is complete, taste and adjust seasoning with salt and pepper as needed.

Ladle the soup into bowls and garnish with fresh herbs or sour cream.