Rubber mats topped with “fine” not “coarse” pine shavings; pick with a fine tine manure basket fork. Easy, peasy.
Simkie, your layout is my dream footing! 
Currently, my run in has stone dust, but no bedding, all graded to drain out and down. I have rubber mats where the pony’s feed tub goes (she drops food) and where the big guy is tied (he paws). But no bedding. The pony mare will use the bathroom in the shed in bad weather if I have put hay in the shed, the gelding has his stud piles so he is a bit odd that way and has never gone in the shed. But the shed is strictly where they are fed their grain, where they are tied (no barn), and where there is shade in the summer and hay in the winter if it is viciously windy or icy. They like to lie down to sleep in the sun or where they can see the whole expanse of the field and road.
I just use cushion sand, no bedding materials in my run-in shelter. Soft, absorbent, drains well, inexpensive to top off every few years.
Do horses use that for a bathroom?
Do you clean the manure out of it?
Nicely done @Sweetums Mom ! Did you secure that front row of mats in some way, so they won’t slide out?
And thank you very much, @B and B! That was one hell of a project, and it tickles me that people get something out of the pics 
I don’t have interior stalls, just this run-in, and I pick manure at each feeding. My gelding rarely poops in the shelter, but the darn mare will come in to poop/pee then go back out to graze.
Yes we did by a million screws…:yes: The only thing I wish we did better was allow for more compaction of the stone dust underneath. We did the small shed first and made mistakes and did better for the bigger shed. What a project! But it was worth every effort/money as cleaning them is a breeze.
