Prepare spice mix according to bag directions. Place a parchment round on the bottom of an 8 inch cake pan that is 4 inches tall. Spray the pan, place prepared mix in pan and bake until cake springs back lightly when touched. Let cake cool completely and de-pan.
While the cake is cooling, place 3 pounds sugar and 3 pounds water in a pan and bring to a boil. Using a slicer or mandoline, slice 5 pounds oranges very thinly while still maintaining their shape. Once the water has boiled, very gently lower the orange slices into the pan. Cover the top of the fruit with a parchment circle the same size as the pan with a little hole cut in the center. The center hole is important as it allows steam to escape while still covering the fruit and allowing it to all cook at the same rate. Bring the mixture to a boil, reduce heat and simmer for 20 minutes. Place the pan in an ice water bath the stop cooking time. There will be extra oranges and syrup!
Heat apricot glaze to boiling, reduce heat to keep warm and free of lumps. Trim belly off cake. Invert cake onto a cake board and brush the sides and top with warm apricot glaze. Arrange candied orange slices around sides and top of cake, working in sections and glazing as you go. If you work too quickly the oranges are sure to fall off so take your time! Glaze will set up at room temperature, once cake is finished and set, place a mound of frozen cranberries on top, decorate with mint sprigs and serve.