Add chopped shallots and garlic, apple juice, strained tomatoes, brown sugar, smoked paprika, dry mustard, and cayenne pepper (if using). Lay the chicken thighs on top, then turn them to coat fully in the homemade sauce.
Place the lid on the slow cooker and cook on high for 2-3 hours or low for 3-6 hours, or till cooked through (an internal temperature of 165°F). Remove the chicken thighs and serve whole, or shred with two forks for a shredded BBQ sandwich. Taste and adjust any seasonings.
Notes
I like Pomi brand of strained/pureed tomatoes. Look for one without seasonings!
Store-bought BBQ sauce can be substituted if desired - use 2 cups.
Temperatures on slow cookers can vary greatly. Mine is usually done cooking these chicken thighs on low within 3 hours!
You can use bone in chicken thighs, they will just add another hour to the cooking time.
In a pinch, you can use high heat and cut the time in half, however, the meal won't be quite as flavorful, and might be a little more dry. Same notes go for using chicken breasts.