Decorate zigzag stripes. Looking down at the top of the cake, use toothpick to mark triangles on bottom edge of cake, 1 in. high x 1 1/2 in. wide at bottom and 3/4 in. apart, starting at 3/4 in. from left edge of cake. Use blue icing pouch with tip 150 to pipe zigzag lines to fill in triangles. Use white icing pouch with tip 150 to pipe four zigzag lines above triangles across the cake top. Repeat with four blue zigzag lines above white lines. Repeat pattern to cover cake top.