To the slow cooker, add the coconut milk, onion, garlic, and seasonings. Stir well, then add the chicken. Cook on LOW for 6-7 hours.
Once cooked, place the chicken on a plate and shred up the chicken. Whisk together the cornstarch and water in a small bowl.
Add the shredded chicken back into the slow cooker along with the cornstarch slurry. Cook on LOW for an additional 20 to 30 minutes to thicken the sauce. Serve chicken and sauce over cooked white rice, sprinkle with cilantro, and serve naan bread on the side.