So I will be getting chickens next Feb, and I already have a 5' by 10' dog kennel to use as a chicken run. I need to know what the best material to put in the run would be. I have a part of my yard that used to be a playground and is all pea gravel, and I have grass in the rest. I won't be moving the run, by the way. I need to make sure it is -low low cost -not really smelly -easy to maintain - I cant have the material all over the yard Would it be best do just put it on grass or just on pea gravel? Maybe hay or sand? Thanks!