As they don't seem to have a base you would need to sit it on heavy wire mesh so that foxes or dogs cant dig under.
Two other things - we have no grass, lots of deck and lots of garden beds where they can roam during the day but no grass for the them to feed on, and we have a small dog. My husband says we wouldn't be able to train our dog to like the chickens but I'm sure they would eventually be able to live together, the dog is an inside dog most of the time but he follows us where ever we go so is generally outside if we are.