Generously season the chicken breasts all over. Using your hands will get the job done most efficiently as you'll cover every inch and the seasonings can be massaged directly into the meat. This generally takes 2-3 tbsp of seasoning.
Add the sliced peppers to the bottom of the crockpot* (see note)
Add the sliced onions and 1 tsp of fajita seasoning.
Mix to coat the veggies.
Place the seasoned chicken breasts on top and add the chicken broth.
Cook for 4 hours on high (or 6-8 hours on low).
Transfer the chicken breasts to a bowl and allow to cool slightly.
Using two forks (or your hands), shred the chicken breasts into small bite sized pieces. Alternatively, you can slice it, if preferred.
Add it back to the crockpot with the rest of the ingredients. Stir and allow to marinate in the juices for about 10 minutes before serving. If you find that there is too much liquid remaining in the bottom of the crockpot after cooking, ladle some out (until there is a desired amount) before serving.
Serve with all your favourite fajita toppings! Enjoy!
Notes
If you prefer crispier veggies as opposed to soft ones, wait until the last 30 minutes to add them.