Ah but you see, the slider is not within the hive to a bee mind! 
It is below the screened bottom board, so they can’t reach it anyway and it isn’t part of the floor that leads to the normal entrance. Your bees will clean anything that they can reach from inside the hive. Everything else is outside and not to be worried about. 
I agree with @Ropate too, that is what I find with my slatted racks.
Very clever @Dawn_SD.
BTW, are your slats parallel, or perpendicular to the frames? I’ve seen designs for both. The parallel being the more modern ones.
Parallel. 
My experience with slatted racks is the same.
We are not looking at major changes to the bee behaviour but they do cope better in hot weather and I suspect they find it easier to regulate cold air flow into the hive in Winter. Not sure if it translates to more or less honey but I believe it improves hive conditions for the bees.
Was also thinking about the shape of the slats and debris (triangles? dowel? etc) but then if cleaning does not seem to be an issue - if I were a bee - maybee I would find it more comfortable to hang out and have a rest on a flat surface with a few mates than balance solo on a curved one.
Hi @Regina and welcome to the Flow forum! 
My bees keep their slatted racks very clean, and they certainly seem to like hanging out on the flat surfaces of the slats when I am inspecting! 
Thank you Dawn. That’s good to hear and encourages me further to get some made up for my hives. The slatted racks seem virtually unheard of in Australia but sound like they would be a very positive addition especially in managing a range of weathers and temperatures. I live on the very bottom eastern coast facing Bass Strait and the Island of Tasmania - so we have very cold just above zero south westerly winter storms coming in from the ocean and up to 40 degrees Celsius (100+ Farenheit?) in the summer. I think the racks will be perfect for my girls. Kind regards.
I’d go for it too Regina - just because it’s unheard of doesn’t mean it’s not appropriate. All my hives have them, with the observable benefits noted. I didn’t hear about them from my instructor nor my original supplier - read about them here! Thanks @Dawn_SD 
Hive mats are not very common here as far as I know, but have some pretty good benefits too.
