Combine all but the last 4 ingredients in a slow cooker and set to low for 5-6 hours, or until chicken shreds easily.
Discard the bay leaf. Remove the chicken from the tomato sauce mixture and shred with two forks. Return the shredded chicken to the slow cooker, stir to combine, and cook for an additional 30 minutes.
Scoop the Chicken mixture into corn tortillas, top with sliced avocado, pico de gallo, and crumbled cotija cheese. Serve warm.