Chunks of other planets, we have always been pretty good at creating explosives previous generations couldn't even fathom so such destructive disposition may get to be a positive thing for once.
I guess you’re thinking of something that orbits earth? If you build something that orbits the sun at the same rate as us then it could just be flat and circular.
Maybe someone smarter than me can calculate the optimal parameters to get the smallest shade that orbits the sun. If we are looking to only block out a percentage of the sun then it doesn’t even need to be fully opaque, maybe a giant dream catcher would be fine.
That means you're heavily restricted in where you can put it. It has to be either right next to earth, in which case it's hard to keep away from Earth, or at L1, which is not stable. There's no other place you can put something where it will stay directly between us and the sun.
It's wildly impractical to try to keep something far from a stable orbit with active thrust long-term. I mean, why don't we all have flying houses? It'd be cool.
You can put something in between, a giant sun shade