Rinse and sort the dried pinto beans, removing any debris. Soak the beans in water overnight or use the quick soak method by boiling them for 2 minutes and letting them sit covered for 1 hour. Drain and rinse the beans before using.
In a skillet, heat olive oil over medium heat. Add the chopped onion and cook for 4-5 minutes until softened.
Add the minced garlic to the skillet and cook for an additional 1 minute until fragrant. Remove from heat.
In the slow cooker, combine the soaked and drained pinto beans, cooked onion and garlic, diced tomatoes with juice, tomato sauce, and vegetable broth.
Add chili powder, ground cumin, smoked paprika, dried oregano, salt, black pepper, and cayenne pepper to the slow cooker. Stir well to combine all ingredients.
Cover the slow cooker and cook on low for 6 hours, or until the beans are tender and the chili has thickened.
Stir the chili beans before serving. Adjust seasoning with additional salt or chili powder if desired.