So, I bought one of those weird, African cape/dress/robe/muumuu things from a thrift store due to its pattern and bountiful amounts of fabric. It's also a pretty thick fabric, good for winter.
The full thing.
You can see the pattern and the button closure better on this one. I just used five panels with a little flare at the bottom to create the little ruffle-like effect at the bottom. Easy as pie!