Heat oven to 350°F (325°F for dark or nonstick pans). Spray bottoms and sides of two 8- or 9-inch round cake pans with baking spray with flour. Make and bake cake mix as directed on box, using 1 cup water, the oil and eggs. Cool 10 minutes. Remove from pans to cooking racks. Cool completely, about 1 hour. Refrigerate or freeze 30 to 60 minutes for easier handling.