Peel and wash potatoes; slice thinly using a mandolin slicer. In a microwave safe bowl, melt butter. Add potatoes to the bowl of melted butter, salt and pepper to taste. Use hands to toss potatoes in the melted butter, salt and pepper, so each potato gets coated well. Place half the potatoes, evenly, in the bottom of a greased 13 X 9 cake pan, sprinkle, evenly, with 1/2 cup of the cheese; Repeat once. Using kitchen shears, or a sharp knife, cut or slice bacon into small bite sized pieces. Cook bacon in a medium to large saucepan over medium-high heat. Once the bacon has finished cooking, drain grease, and reserve 1 Tbsp. of cooked bacon for the top. Add milk, ranch packet, and flour to the saucepan of cooked bacon. Still on medium-high heat, wait for the milk mixture to come to a boil, whisking often. As soon as milk mixture comes to a boil, turn off the burner, and carefully remove it from the heat, pour evenly over top the cheese and potatoes. Cover with foil and bake at 425 degrees for 50 minutes. Take foil off, and evenly sprinkle 1 Tbsp. of the reserved bacon and the last 1/2 C. of cheese. Bake and additional 10 minutes or until cheese gets brown and crispy.