1. Spread about half the mayonnaise in a layer on the bottom of a 10- x 16-inch pan.
2. Arrange two layers of sliced potatoes, sprinkling with half of salt, paprika and pepper.
3. Place flounder fish fillets over potatoes. Spread a layer of mayonnaise over fish.
4. Season with remaining spices.
5. Bake in covered pan for one hour at 375–400 degrees Fahrenheit. Serve hot.