Can't help you because your universe is inconsistent...
"The other worlds are easy as pie, since gravity is flat, they are too, more or less."

So the shape of the planets in your universe are disks.

How does a sphere get created then?

Assuming it still does, it's just a stack of discks with a hole in them. Each "disk" would then be mapped top down as individual with disk layers.

the overall shape of the multi disked thing is inconsequential and the pieces are only dependant upon that particular layer and how it broke up...

Let's say somehow the laser created an explosion which cracked the planent a star shape... Layer 0's North star point would be disconnect from Layer 1's because even though it's the same shape there's still the fact that they're different disks.

Also if you hit this things from the top with laser beam that reached the center and then exploded, the bottom be greatly unaffected, but also the pressure wave would fire back through the open spaces and try to escape so that if you essentially had cylinder with thick top and bottm, then the sides would break out, separating the top and bottom in at least one place through creating a hole. The pressure from this weapon would travel back upwards and outwards, but the lower level wouldn't be wholy unaffected because it would have chuncks of the above rocks slamming down on it.


So... What I'm saying is that for what you're describing your shape is completely off