1. Heat the oven to 350 degrees F. Peel potatoes and divide in 3 portions.
2. Liberally grease the bottom and sides of a 9x13x2-inch casserole.
3. Place one-third of sliced potatoes in bottom of casserole and dot with half the butter. Spread 7 slices of ham, 5 slices of cheese, and half the onions on top of potatoes. Sprinkle with 2 tablespoons flour and salt and pepper to taste.
4. Repeat layering with second portion of potatoes.
5. For last layer, add third portion of potatoes and remaining cheese slices over top. Salt to taste.
6. Pour milk over layers (it should show when casserole is tipped slightly to one side).
7. Bake until potatoes are tender, about 1-½ hours. Precise timing is not important (another 20 minutes won’t hurt). Bake uncovered or cover loosely with foil for the first 40 minutes.
8. Tie up tightly and place in a basket.