Likely these OS Hubs will all be situated inside of existing US or coalition bases. This covers the need for force protection, utility services and access to air or sea ports.
If you want to see where they could or will go, check out major US bases in these areas. We will most likely piggyback off them. No doubt they will open on an as-needed basis during medium to large operations and remain open following the end of the operation on a minimal caretaker status. This way the cost of setting up the base can be rolled into the operational budgets that are often specially assigned outside of the general DND budget.