Bricks, concrete blocks or patio pavers will work if you have access to any of those. If a fox (or other predator) can get inside the barn it can dig under the coop from inside (not just the run)
I had my coop built when my chicks arrived but I was racing against the clock to finish the run and apron.Locking them in a secure coop at night doesn't require any lights or hardware cloth on the run. As a temporary measure during the day use electric poultry fencing around the run and double...