It may be best to wait for an official response to this, but this is how I've handled it: in previous years, I've treated it like just another story. The story takes place in and revolves around the setting and involves sensory description of whatever place I've chosen, but usually I have characters moving and acting in the setting, too (hopefully in meaningful ways that allow me to explore extra facets of whatever place I've chosen)!

I hope that's helpful. Good luck writing!

I'm attempting to work on my setting description right now, too.