Combine 1/2 cup flour, salt, and pepper in a bowl; mix well. Dredge chicken in flour mixture. Place chicken in a 5-quart casserole; pour melted butter and boiling water over chicken. Cover and bake at 350° for 1 1/2 hours. Remove cover, and continue baking 15 minutes or until chicken is brown, basting occasionally with pan drippings. Remove chicken; set aside, and keep warm. Reserve 1/4 cup pan drippings.
Combine remaining flour and reserved pan drippings in a skillet, stirring until smooth. Cook 1 minute over medium heat, stirring constantly. Gradually add 2/3 cup water, stirring well; cook, stirring constantly, until thickened and bubbly. Stir in lemon juice. Place chicken on a bed of rice on a serving platter, and pour gravy over top.