Stir tomato sauce, chiles, vinegar, honey, paprika, tomato paste, Worcestershire sauce, mustard, ground chipotle and salt in a 6-quart slow cooker until smooth. Add chicken, onion and garlic; stir to combine.
Put the lid on and cook on low until the chicken can be pulled apart, about 5 hours.
Transfer the chicken to a cutting board and shred with a fork. Return the chicken to the sauce, stir well and serve.