Heat oven to 180°C (160°C for dark or nonstick pans). Grease bottom and sides of 33x23cm pan or spray with baking spray with flour. Make and bake cake mix as directed on box for 33x23cm pan. Cool 10 minutes; remove from pan to cooling rack. Cool completely, about 1 hour. Refrigerate or freeze cake about 1 hour or until firm.
Cut cake as shown in diagram. Arrange pieces to form sailboat on tray. Tint 300 grams frosting with yellow or brown food color for hull. Spread a thin layer of white frosting over top and sides of sails, and a thin layer of tinted frosting over top and sides of hull, to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes to set frosting.
Frost entire cake with remaining frosting. Cut licorice pieces to desired length for the mast; place near the edge of the longest sail. Use candy for portholes, or decorate as desired. Store loosely covered.