Rub a little oil on the bottom of your slow cooker. Add diced onion, followed by the chicken breasts. Top with spices (cumin, salt, pepper). Pour diced green chiles and any juice in the can over the chicken.
Cook on LOW for 4 hours or until chicken shreds easily with a fork. Remove chicken from slow cooker and shred with two forks or in a stand mixer, return to slow cooker with liquid. Adjust seasoning to taste. Serve and enjoy!