Advice for the run and surface type

[MiyuChickens]

Hello all...My first post here. I am in the middle of building a Wichita Cabin coop and had a question on the surface of the run. The coop is overall 5x10 and we plan to get 5 chickens. For the base I started by digging out the grass and building a base with center blocks and then 2x6 on top of the blocks. So I basically have about 12 to 14 to fill up for the run. I was going to start with the bottom layer as some sort of riverbed rocks/pebbles and then add the surface that the chickens will on from there. What is best to use here. ie. play sand, cheap dirt, gravel clay...

See photo to make more sense... hard to explain. basically, what is best the chickens to run around on and good for drainage.

thanks ryan

 

[animalwild]

I used to just have grass but when it rained it was a mess now i use sand in my run and coop and I love it it's what I would highly recommend.