In a bowl, mix the fajita spice mix and set aside. Reserve 1 Tbsp of the mix for the vegetables. In a second bowl, add the sliced chicken, salt and pepper, and the remaining fajita spice mix. Mix to combine.
In a bowl, combine the diced red onion, diced tomato, chopped coriander, and lime juice. Add the avocado and mash or mix through to your preferred texture, chunky or smooth. Season with salt and pepper and set aside.
Add the washed rice, cold water, and salt to a saucepan. Bring to a boil, reduce the heat to low, cover, and cook for 12 minutes. Turn off the heat and leave covered for 4–5 minutes. Remove the lid and fluff with a fork. Add the drained black beans and chopped coriander and mix to combine.
Place a large, high-rimmed pan or pot over medium-high heat. Add 1 Tbsp (20ml) of avocado oil and, once hot, add the onion and bell pepper. Sauté for 6–8 minutes, mixing regularly. Add the reserved 1 Tbsp of fajita spice mix and cook for 1 minute. Remove and set aside.
Place the same pan back over medium-high heat. Add the remaining 1 Tbsp (20ml) of avocado oil and sear the chicken for 4–5 minutes, or until golden and the internal temperature reaches 74°C (165°F). Add the oregano and the onion and bell pepper mix back to the pan and cook for 1 minute. Remove from the heat.
Slightly warm the tortillas and spread with the guacamole. Add the black bean and coriander rice, and top with the chicken fajita mix. Wrap tightly, tucking in the sides of the tortilla.