Dwarves remove foundations from below mounted windows as soon as possible:
Do you remember 24 z-level high megahole in the eastern edge of the map? It's been walled out:
I wondered: is it possible for creatures to walk on a levitating surface? Dwarves dropped a puppy onto a flying window, unexpectedly he fell through the upper surface, now he stands on the lower surface, inside the window block:
Later dwarves built an obsidian floor nearby, the puppy made it through the sidewall and walked away.
A mercenary dwarf bit porcupine's head off just like Ozzy Osbourne did it to a pigeon:
Next experiment, a dog has been dropped onto the flying window from a higher place:
This time he stands on top of the flying construction correctly. But he still can't walk until there's a normal floor nearby.
Main glass constructions grow slow but steady:
Goblin mercenary Amak Cegadocda showed a master-class of martial arts:
He bit a weregilamonster in the head and then hacked this head off when it was still in his mouth. He's a great warrior.
Then he attacked a herd of wild muskoxen, he's like a chainsaw, he can hack muskox's body apart with a single strike:
Dwarves dropped few buckets of water over flying windows and then, when water froze, dropped a puppy over it:
Then I noticed that the ice had touched a floor that dwarves built nearby during experiments. It broke levitation state of the ice and when dwarves dismantled this floor, the icy part of the construction collapsed:
So now I know how to build flying islands in Dwarf Fortress. I suppose that this fort will be the fort of flying !!science!!.