Preheat oven to 350°F. Spray a 7×11"or even 9×9" baking-dish with cooking-spray.
In a large-bowl, then put in the potatoes, cream of chicken soup, sour-cream, cheddar-cheese, garlic-powder, pepper and salt. Stir till well blended and the potatoes are evenly coated.
Pour the potatoes to the baking dish & spread them out into an even layer.
Put the corn-flakes in a plastic-food storage-bag and seal the bag then use the hands to squeeze the bag and crush corn flakes.
Pour the crushed-corn flakes to a small-bowl. Then add the melted-butter. Stir to coat the cereal.
Spoon the corn-flakes evenly over the potatoes and bake uncovered for 35 minutes and let cool 5 minutes before serving.