Tie a red or green ribbon around the base for a scarf (or use red and green fondant squares), then use black fondant circles (or Maltesers) to make the eyes and mouth. Knead a bit of the leftover white fondant icing used to cover the cake with some red and yellow food colouring until you reach an orange colour, then shape into a cone for the nose. Roll out some red icing into a long rectangle, then smooth it over part of the top and some of the side of the cake for the hat. Trim off any excess. Use green icing to shape a bobble for the top of the hat.
Roll out red, green and white icing and use cutters for holly leaves, snowflakes and flowers to stamp out shapes. Using a bit of water as glue, secure some of them into little clusters around the cake. Roll small bits of red fondant to make holly berries.
Roll green fondant into a cone shape, then roll small amounts into teardrop shapes and attach to the cone. Top with little stars made from yellow fonddant and add a few small squares as presents.