I'm not sure what Mayday's axedwarf looks like but I've designed a few architectural megaprojects (Castle forts, vertical murals on walls, that sorta thing)
There are two good options for designing a 3D megaproject - one is to build it in lego or something similar, then you can pull your model apart into "slices" and build it from the ground up. That's a really easy way, if you happen to have lego, which I don't. The other way is to draw an "orthographic projection", or more simply "front, side and top views". Go into MSPaint, zoom to maximum, then draw the front view in pixels. Then, draw side views with the front as a guide, then work out the top from the front and side (just a matter of counting the pixels at that point).
Once you have all the information laid out this way it's fairly easy to work out the shape of each z-level and build or remove material as needed.
here's an example, for a 15 z-level statue of a dwarf holding an axe. Colors are for clarity. I just did this hurriedly in paint so it's probably covered in errors.
So obviously to cast this particular thing you'd make yourself a cuboid block of obsidian 17 by 8 by 15 z-levels tall, then get the miners to remove everything that isn't dwarf. Adapting the design along the way to remove all the mistakes in it.
Is that any help?