Hi Sam,
As long as the resource records are all in the same repository, you can do that. It's one of the great aspects of the ArchivesSpace container module.
Once you've created the top container via the container instance in the first resource record, you can find it by using the Browse option in container instances in the other resource records. Note that when you browse, it will default your search to your current resource record, so you'll have to clear that search.
We use unique identifiers for our shared boxes (e.g., SSC Shared 10), but you can also differentiate by barcode.
All the best,
Dan