1ST STEP – Melt the butter in a small saucepan over medium-low heat. Add the flour, salt, and pepper to the melted butter until the flour dissolves.
2ND STEP – Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard fat.
3RD STEP – Preheat the oven to 350 degrees F (175 degrees C)
4TH STEP – Spread a layer of meat sauce on the bottom of a 9×13-inch baking dish.
5TH STEP – Bake in preheated oven for 45 minutes. Remove foil and continue baking until cheeses are melted, about 10 minutes more.
Let lasagna rest 10 minutes before serving.