Begin by preheating your oven to 350°F (175°C) to prepare for baking.
In a large mixing bowl, combine the shredded chicken, cooked rice, black beans, corn, diced tomatoes with green chilies, salsa, ground cumin, chili powder, and garlic powder. Stir the mixture well until all ingredients are evenly distributed.
Take a 9x13 inch baking dish and layer two of the flour tortillas to cover the bottom evenly. If necessary, trim the tortillas with kitchen scissors to fit the dish perfectly.
Spread half of the chicken mixture across the tortillas in the baking dish, ensuring even coverage. Follow this with half of the shredded cheddar and Monterey Jack cheeses, sprinkling them generously on top.
Add another layer of two tortillas on top, then pour the remaining chicken mixture over the tortillas, smoothing it out evenly. Finish with a layer of the remaining cheeses, making sure to cover everything nicely.
To keep the moisture in, cover the baking dish tightly with aluminum foil and position it in the oven. Bake for 25 minutes.
After 25 minutes, carefully remove the aluminum foil. Return the casserole to the oven and bake for an additional 15 minutes, or until the cheese is bubbly and has developed a light golden tint.
Once fully baked, remove the casserole from the oven and allow it to cool for about 5 minutes. This will make slicing easier.
Before serving, enhance the dish's appeal by garnishing with freshly chopped cilantro. For an additional creamy touch, serve with a delightful dollop of sour cream, if desired.