The easiest poop boards to clean are a single level about waist high(pic below).
Not sure that would work for you.
You might remove that lowest roost so you can reach the floor under there better.
You could put trays on floor that slide out for easier cleaning.
How did you make out? I'm trying to design a droppings board too and like the "boot tray" idea. I was thinking of using a crazy carpet for ease of cleaning (old vinyl flooring would work too) and I want to add a drop-down hatch door to just scrape the droppings off into a bucket.