Heat avocado oil in a large skillet over medium-high heat.

Add the diced onion and sliced celery and cook, stirring often, for about 5 minutes.

Add the minced garlic and cook for about 30 seconds, then remove from heat.

Add the chili powder, cumin, and dried oregano to the skillet and stir well.

In a large bowl, combine the cooked rice, pinto beans, corn, diced tomato, minced chipotle pepper, 1/4 cup of enchilada sauce, and the onion mixture.

Stir well and season with salt and pepper to taste.

Cut the tops off the bell peppers and remove the seeds and ribs.

Fill each pepper with the rice mixture, packing lightly.

Optionally, fill halfway, add a small amount of cheese, and then finish filling.

Place the filled peppers in the slow cooker.

Add about 2 cups of water (1/2 inch) to the crock, being careful not to get water inside the peppers.

Cook on low for about 4 hours.

About 15 minutes before they are done, add a layer of shredded pepper jack cheese to the top of each pepper.

Let the cheese melt and finish cooking.

Serve the peppers with the remaining enchilada sauce and extra cheese, if desired.