In my experience, frames with stores are targets for robber bees, mice, waxworms, beetles, and other pests, so I store any frames that have honey, nectar, or pollen in big plastic bins. Given that this is temporary, just storing the frames in the boxes might be fine, especially if your barn is pretty tight. I would NOT crisscross the stacks though, I would stack them as tightly as possible. Otherwise, robbers and hive pests will find them quick and destroy them. I would also avoid if possible leaving uncapped nectar out, as that will just absorb moisture from the air and ferment.