Peel 4 potatoes and slice thin rounds. Place rounds into a bowl and season them generously with salt and black pepper. In a bowl or large measuring cup, combine with a whisk, 3 cups of milk and 2 tablespoons of flour. Pour milk mixture over potatoes. Set aside for a few minutes while you get everything else ready.
Cover aluminum foil and bake for another 30 minutes (to finish cooking the potatoes.)
Just a little heads up here. I didn't know things would bubble over. I would suggest covering a cookie sheet with foil and spray with non-stick cooking spray (for easy clean-up) and placing the casserole dish on the cookie sheet. It will keep the bottom of you oven clean.