That looks great. Bet your chickens will have some fun with that!Do you have a picture of your run, is it a walk in run?
I would use tree trimming chips. If you can't get those, use untreated mulch. You can also add yard and garden waste, pieces of tree branches (thick and thin) dried leaves. Think of a nice mulched flower bed, where the water drains down into the ground, through the mulch. The poop will filter down through the chips and break down. As long as your run drains fine and doesn't have standing water, this will work well for you. Others on here use deep or semi deep litter and don't have covered runs and it works well for them and doesn't smell. If it would start to give off odors, that's an indication that more stuff should be added to your run.
My run is covered, but here is a picture after I just added yard and garden waste in the fall.
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