Pierce duck skin in several places with a sharp knife. Sprinkle 1 teaspoon seafood seasoning inside duck. Rub remaining 4 teaspoons seafood seasoning over skin. Refrigerate duck, uncovered, 8 hours to overnight.
Preheat oven to 375 degrees F (190 degrees C).
Layer potatoes evenly in the bottom of a roasting pan. Place duck on top.
Roast in the preheated oven until skin is browned and crisp, about 2 hours 15 minutes. Remove from oven and cover with aluminum foil. Let rest for 15 minutes. Carve duck and serve alongside potatoes.
