Heat the olive oil in a frying pan over a medium heat. Add the chicken skin side down and cook for 3-4 minutes until starting to turn golden. Transfer to the slow cooker.
Add all of the barbecue sauce ingredients to the slow cooker with the chicken and stir to coat everything. Put on a low heat for 7-8 hours or a high heat for 3-4 hours.
When the chicken is cooked, use two forks to pull the meat apart until it is shredded. Remove the bones and any gristle. Let the meat sit in the barbecue sauce while you prepare the burrito fillings.
Ensure that the cheese sauce is hot. Destone and dice the avocado. Dice the bell pepper and jalapeños.
To put the burritos together, lay the tortillas out on a work surface. Divide the lettuce, rice, chicken, cheese sauce, avocado, bell pepper and jalapeños equally between all of the tortillas. Wrap the burritos, then heat them quickly in a dry non-stick frying pan until golden. Serve immediately.