A good idea would be to write about something else (similar) and include a backlink to the hub. For example:
Lets say your hub sells iPhone cases. The backlink posts could be about the top five ways iPhone's break. Then include a part at the beginning or end or somewhere saying that a simple iPhone case will protect it. Put your backlink in there.
I didn't go to look at your hubs or anything, otherwise I could probably help you come up with ideas. Just be creative. Shoot me a message if you need help with ideas or something.