Arrange the potato slices in a single layer on a rimmed baking sheet. Bake the potatoes, turning once, for about 20-25 minutes or until they’re tender and lightly browned. Remove the pan from the oven and add the shredded cheese to the potato rounds. Bake for another 5-8 minutes or until the cheese is melted. Sprinkle on the scallions and bacon, if using. Serve with a dollop of sour cream.