Best solution for the ground of my coop :)

Hi Everyone!

We have moved our chicken coop and run (2.6x 2.6) on to the cement area near our house, to avoid any animals digging and harming our girls.

When we are home we let them roam free around our garden. But when we are at work, the girls are kept in the secure coop & run.

I need your help, what should I put on the ground?

At the moment here in Brisbane (Australia) we are experiencing quite a lot of rain.

There is no drainage because it is on cement, so when it rains there is a bit of water that pools in the center of the run.

I had sand in there for a bit but it began to stink. I also tried wood chips but the girls didn't seem to like it and it became fairly soggy.

Should I try a courser sand? Will is smell?

Thanks for your help