Place the chicken and BBQ sauce into the slow cooker. Stir well so that everything is coated. Flatten everything as much as possible.
Pop the lid on and cook for 2-3 hours on high or 3-6 hours on low.
Once cooked, remove all the chicken from the slow cooker and transfer to a plate or board. Shred using 2 forks.
Add the cornflour to the remaining sauce in the slow cooker and quickly stir vigorously until free of lumps. It should instantly thicken to the consistency of gravy, but you can always heat it in the slow cooker for a few minutes until it thickens to your liking.
Return the shredded chicken to the slow cooker and stir until all is well coated.
Serve up in gf brioche burger buns with slaw or in crunchy taco shells with lettuce, slaw and smashed avocado. Serving with extra BBQ sauce is highly recommended!