Creating the Easy Chicken Pot Pie Casserole can be straightforward if you follow these simple steps:

1. Preheat your oven to 375°F (190°C). This ensures the casserole cooks evenly.
2. Mix the Filling: In a large mixing bowl, combine the cooked chicken, frozen mixed vegetables, cream of chicken soup, milk, garlic powder, onion powder, thyme, salt, pepper, and cheddar cheese. Stir until well blended.
3. Prepare the Baking Dish: Lightly grease a 9×13-inch baking dish with cooking spray or butter.
4. Pour the Filling: Transfer the chicken and vegetable mixture into the prepared baking dish, spreading it out evenly.
5. Roll Out the Dough: If using crescent roll dough, unroll it and lay the dough over the filling, pressing the seams to seal. If using pie crust, lay it out and slice vent holes in the top.
6. Bake: Place the casserole in the preheated oven and bake for 35-40 minutes or until the crust is golden brown and the filling is bubbling.
7. Cool Slightly: Once baked, remove the casserole from the oven and let it cool for 5-10 minutes before serving.

These steps will guide you in preparing this incredible casserole with ease.