Wash hands with soap and water for 20 seconds.
Preheat oven to 350°F.
Combine all ingredients for the crab filling, except for the egg, and stir well to combine.
Add the egg and fully incorporate it into the mixture.
Season the flounder on both sides, as desired.
Stuff approximately 1/4 of crab filling into the center of the flounder filet.
Roll flounder with the crab mixture in it. Alternatively, the filling can be placed on the flat fillets and not be rolled up.
Wash the counter and utensils that touched the raw fish. Wash hands with soap and water after handling raw fish.
Bake the fish for 20-30 minutes until it reaches an internal temperature of at least 145°F on a food thermometer. Do not overcook the fish.
While the fish is baking, prepare the garlic cream sauce.
Turn on the oven broiler, and broil for 4–5 minutes on high or until browned.
Remove the flounder from the oven.