Nice build.I have 4 Wyandottes, 1 Ostralorp, 3 RIR, 1 Buff Orpington & 3 Mottled Javas. The Wyandottes and my Ostralorp are the ones that really roost in there. The rest sleep out in the run.
And perhaps "slots" wasn't the right word. Attached is a photo to better explain/give perspective.
You have a good point on acclimation to their environment. Next winter I want to figure out a better plan for a warm space that excludes the need for a heat source. This one isnt quite it. Figuring it out as I go along.
I should mention that this behavior of the hens sleeping out in the run started recently. Before then they always went to the roosts in the hen house!
First photo is an outside view which leads to 2nd & 3rd photo being where ventilation spaces are. 4th pic is the roosts/hen house so you guys can see what I'm talking about