You would likely need to obtain the material via ... https://en.wikipedia.org/wiki/Star_lifting https://en.wikipedia.org/wiki/Star_lifting and possibly large

You would likely need to obtain the material via ... https://en.wikipedia.org/wiki/Star_lifting https://en.wikipedia.org/wiki/Star_lifting and possibly large scale transmutation. Disassembling the gas giants might be enough for some designs. My understanding is that it isn't physically possible to construct rigid spheres or rings in that orbit, so it would be an orbital swarm of some kind, with the elements able to actively correct for the inevitable perturbations.