1.Preheat Oven To 325 Degrees F (165 Degrees C). 2.Place Smoked Haddock Into A Glass Baking Dish. Whisk Flour Into The Melted Butter Until Smooth, Then Whisk In Milk, And Pour Over The Haddock. 3.Bake In Preheated Oven Until The Sauce Has Thickened, And The Fish Flakes Easily With A Fork, About 35 Minutes.