Hi Confusedturtle,
wow, I'm interested in this too.
I got a giant flower pot saucer -- It was about 13" across and maybe 2 or 3 inched deep. I put some silt-like dusty dirt from our washout in the road into it, and stuck that in their run, because I move my coop and run daily and they are always on grass. (I also have three hens). They loved it. But, due to the shallow sides and the vigorous dusting they gave themselves, they threw the dirt out everywhere...eventually when they stepped on the edge they tipped the rest out.
Next I am going to try a dishpan--like you put in the sink...Rubber maid is one manufacturer.... I have some "play sand" now, and can dig/scoop some of the same dusty silt that I had before. I am going to add a cupful or two of DE. The sides will be taller, so perhaps the contents won't be thrown out as quickly. I think that if you have any cold ashes that is another recommended additive.
It soiunds like you will have a really nice sized 'sandbox' for your hens to dust in. Because your space is so much larger, the depth of the sides may not be any problem at all. You should go ahead and give it a try and post back the results, unless some other Back yard chickeners have expereince that would point to the contrary.
In the meantime, my hens will still try to dig up all the grass, get down to the dirt and flop in it and try to dust-- it is very hot here now..so it must give them some relief--- Maybe even more than a dust bath would-- they have varying degrees of success...with their excavations, and then whooosh the run and coop get moved again (like a chicken tractor).
Glad that you posted this -- I'm going to get that old dishpan out and fill with dust and sand and DE.
