1. Cut chicken along the backbone with a sharp knife or poultry shears. Discard backbone. Place chicken breast side up. Press down on breastbone to flatten slightly. Transfer chicken to a 13x9-inch ( 3 quart rectangular) baking dish.
2. Brush 1 tablespoon oil over entire chicken, then sprinkle with 1 teaspoon salt, cumin, and red pepper flakes. Pour lemon juice over top and add lemon halves to dish. Place chicken in the refrigerator. Marinate 1 hour, turning chicken once.
3. Arrange oven racks in center and lower third of oven. Heat oven to 425 degrees F. Bake chicken skin side up on center rack, 1 hour 15 minutes or until cooked through, basting twice.
4. Meanwhile, for the potatoes, toss potato slices with 1 tablespoon oil and 1 teaspoon salt in bowl. Arrange 4 long rows of slices, overlapping slightly, on a large baking sheet. After chicken has baked 35 minutes, add potatoes to lower oven rack and bake 40 minutes until potatoes are tender and edges are golden.
5. Transfer chicken to a cutting board. Cut into 4 pieces. Arrange pieces on 4 serving plates. Skim fat from pan drippings. Serve chicken with drippings, potatoes, and green beans. Makes 4 servings.