Spray an 8x8-inch casserole dish with nonstick spray.
Place a single layer of potatoes (overlapping a bit) in the prepared dish. Sprinkle some of the flour mixture on top. Sprinkle cheese on top of the flour mixture. Repeat layers until you've used up all of the ingredients (ending with cheese).
Pour the hot milk over everything. Dot the top of the scalloped potatoes with butter. Sprinkle with paprika.
Heat, uncovered, in the microwave for about 15 minutes- or until the potatoes are tender and the cheese is melted. Turn the casserole once or twice while cooking.
Serve with some chopped green onions sprinkled on top.