Preheat oven to 425°. Spray shallow 2-quart baking dish with no-stick cooking spray; set aside.
Melt Country Crock® Spread in medium saucepan over medium-low heat. Whisk in flour and cook, whisking constantly, 1 minute. Whisk in milk and salt and bring to a boil over medium-high heat, whisking frequently. Reduce heat to medium-low and simmer, stirring occasionally, until thickened, about 5 minutes. Remove from heat and stir in cheese.
Arrange 1/2 of the sliced potatoes in prepared baking dish. Pour about 1/2 of the sauce over potatoes. Repeat with remaining potatoes and sauce. Bake covered 30 minutes, then uncover and if desired, sprinkle with additional cheese. Bake uncovered 25 minutes or until potatoes are tender