Depending on how big you want it:

cut rectangles or bake in rectangular pan and stack however high you want it to be, say 3 or 4 layers. I'd support every 2 layers with a cake board and dowels.

Place your bottom cake board on a block that's somewhat smaller than your board so it looks like it's got space under it. Make gumpaste legs for each corner.

You could ice the sides in basketweave or fondant. Do a canopy over the head if you like using fondant or gumpaste dried over something round like a coffee can or round object of appropriate size. Once dried it should sit on the top of the cake and you can hide the edges with a decorative border.

Maybe make a fondant blanket to drape over the top.

My buttercream is the powdered sugar, butter and shortening type, and it usually lasts about a week or so at room temp and about 1 mo to 6wks in the fridge.

You probably shouldn't bake it much earlier than 2 days before it's due unless it will be covered 100% in fondant, then you have another day.

HTH-