if you have the oval pan from course II (?) that in a double layer (4" tier) serves 13.
so 3 of those stacked give you 39 servings and a 12" height just for the top part (tube?) of the boot
then there's the foot part to add.
diagram shows 3 - 4" oval tiers on a built up base of cake
really -- the biggest problem will be that dang heal and sole of the shoe. (the deep purple part in the diagram) the itty bitty drawing is looking straight down on the shoe -- to show how it has pointed toe -- i'd get a real boot and just trace around it for shape
make the heel and sole out of wood or built up layers of foamcore or cardboard or....???
then start stacking cakes. use sheets split in half for foot and the ovals for the "tube" (just what is the real name of that part of the boot?)
the "tube" part of the boot is just a multi-tier cake, like any wedding cake, only all tiers the same size.
most of the carving will be on the foot section.
the orange section can be all icing or "cake spackle" - cake mixed with buttercream like going to make cake balls but use to fill in the area instead
wrapping in fondant will be a bit of a task -- but -- there I'd take my cue from the construction of a real boot and do it as a series of overlapping pieces (just like real leather on a real boot) smaller pieces to work with and can cut them to conform better to the shape.
HTH you visualize it.