I suspect this baker used 2-3 layers; a combination of 8 & 12" diameters??
I too would love to hear from the designer! As for myself, I find it helpful to select a pan larger than, but nearest to the finished size and shape of your creation…
For example, in my armadillo cake (which I will post) I selected a Dutch oven and domed Dutch oven lid to bake in as opposed to the recommended football cake pan…
It allowed me to fill, then carve the frozen layers more accurately.
Also, do not overlook the idea of “cake molding”- in which a gently warmed layer is slowly “bent” into shape, then plastic wrapped in place until cool. This I did for my armadillo’s domed shell, and it worked very well!
I hope this helps others- the carved road cake is adorable and very well done!
The biggest tip I know for carving cakes is this: use moist recipes, ALWAYS carve frozen, and don’t be afraid to refreeze pieces if needed.
K. Downer