Having kept hens for approx 20 years, i would say introduce during the night ~ let them wake up with each other but they must have alot to do in the morning, loads of food and water with lots of hanging cabbage/lettuce, bowls of spaghetti, cut grass sprinkled everywher ~ anything to detract attention from each other, the less time they have to spend worrying about pecking order, the less time they will spend finding the correct order!!! Good luck