In advance, use tip 104 to make 30 white Ribbon Roses. Make extras to allow for breakage and let dry.
Bake and cool 8 x 3 in. round cake. Use spatula and ivory icing to ice cake smooth. Use tip 3 and white icing to pipe dots in loops shapes about 1 1/2 in. apart from loop points, on cake top and about 1 in. apart from loop points on sides. Use tip 12 to pipe mound of white icing on top center of cake and position 7 Ribbon Roses on top of mound. Use tip 21 and white icing to pipe shell bottom border. Attach remaining Ribbon Roses on top of shell border.