Use serrated knife to cut one-fourth off each cake to form a straight edge about 7 inches long as shown in diagram (discard small pieces of cake or save for another use). Spread about 2 tablespoons frosting on bottom side of 1 cake. Place bottom side of other cake on frosting, matching cut edges. On serving plate or tray, stand cake, cut side down. Cover; freeze 1 hour or until firm.