In a mixing bowl, combine ¼ cup of mayonnaise, one beaten egg, the juice and zest of half a lemon, and a tablespoon of chopped parsley. Season with a teaspoon of Old Bay seasoning. In a separate bowl, gently mix together 1 cup of lump crab meat and ½ cup of tiny shrimp along with ½ cup of bread crumbs. Carefully fold the crab and shrimp mixture into the mayonnaise mixture until well incorporated.

Preheat your oven to 350°F (175°C). While the oven heats, take a 9x13 inch casserole dish and generously butter the bottom and sides to prevent the stuffed flounder from sticking.

Lay the flounder fillets on a clean surface, with the flesh side facing up. Spoon about a tablespoon of the crabmeat stuffing onto the center of each fillet, then gently roll the fillets from one end to the other, securing the stuffing inside. Place the rolled fillets seam-side down in the buttered casserole dish.

Melt 2 tablespoons of butter in a small saucepan over low heat, then stir in the remaining lemon juice. Brush this buttery mixture generously over the stuffed flounder, ensuring each roll is coated. Finally, sprinkle a dash of paprika over the top.

Carefully place the casserole dish in the preheated oven and bake the stuffed flounder for 15-20 minutes. The fish is done when it turns opaque and flaky.