I finally finished it! It seemed like it took way too long but here it is. I used eight 45 degree triangles, so I'm not entirely certain why it didn't exactly work out to a complete circle, but it looks great under the tree anyway.
Skirt was strip-pieced from my stash. I added the spokes to make it larger since it seemed like it would be much too small. Total diameter is about thirty inches. Good thing our tree is so tiny! It works out great for our tree but would be much too small for a larger one.
I plan on finishing the surcoat I've been working on next.