For this one, bake a rectangle cake, and smooth the corners out once it’s cooled. Apply jam, and lay a thick layer of green fondant icing over the cake. Cut a stencil of a number out of paper, and use this is a guide to cut the number out of a sheet of gray fondant. Use white fondant for the road markings, and white and black fondant squares to make a start and finish line. All the additional details can either be made yourself or bought from cake stores, depending on your confidence; fondant cars, flowers and letters are inexpensive, and will finish the look perfectly.