Slice the top off each pepper, save the tops and pop out the stems. Remove seeds & membranes from peppers, do not puncture the bottoms. Dice the tops.
Saute the chicken in a non stick skillet for 5 minutes with just a small splash of olive oil, remove from the pan (not trying to cook them through, just giving them a head start).
Same pan, saute the onion until transparent, about 3-5 minutes.
Add the cumin, chili flakes, salt and pepper to taste, and mix in, then add the chicken again, then the rice, corn, chopped tomatoes, and the chopped pepper tops. Mix to combine and remove from heat.
Fill each pepper with the mixture and place in the slow cooker. Any extra meat mixture left over, pack that around the peppers.
Add the chicken stock to the slow cooker and turn on Low for 5 hours and cover. Do not open the lid unless you see no liquid in the pot, just add another cup of water then.
Serve and enjoy.