Coat a slow cooker with cooking spray.

In a small bowl, combine brown sugar, cumin, chili powder, dried oregano, ancho chili powder, cayenne pepper, smoked paprika, chipotle chili powder, salt, and pepper.

Rub half of the spice mixture over the chicken breasts and thighs.

Set chicken and the remaining spice mixture aside.

Heat 2 teaspoons of olive oil in a large skillet over medium-high heat.

Add chicken in batches and brown for 3-4 minutes per side.

Transfer the browned chicken to the slow cooker and repeat until all chicken is cooked.

Heat the remaining 2 teaspoons of olive oil in the same skillet.

Add diced yellow onions and cook until browned and softened, about 7-8 minutes.

Place the cooked onions on top of the chicken in the slow cooker, then add the diced green chilies.

In a separate bowl, whisk together orange juice, tomato paste, lime juice, cider vinegar, minced garlic, hot sauce, and a dash of black pepper.

Pour the sauce mixture over the chicken and vegetables in the slow cooker.

Cover and cook on low for 6-8 hours, or on high for 4 hours, until the chicken is tender.

Transfer the cooked chicken to a cutting board and shred it using two forks.

Place the shredded chicken in a bowl.

Add sauce from the crockpot to the shredded chicken until it is moistened to your liking.

Serve the shredded chicken in warmed corn tortillas with your favorite taco toppings such as avocados, cheese, cilantro, and additional sauce, if desired.