Hey Zach, luckily enough, I was actually researching this most of the night.
The one thing that kept popping up over and over again, was to get a picture of a clownfish hosting in an anemone and then tape it to your tank, so your clownfish can see.
I know it sounds silly, but alot of people said it worked for them. Other than that, there really isn't anything you can do. You have to be patient and let things take there course. Multiple accounts of people buying anemones and their clownfish never hosting them. Also, many people have their clownfish host in everything, except what the owner wants them to host in, ie powerhead, shrooms, LR, Brains, etc.
Just be patient and hope for the best. Also, the best is that the clownfish feels safe and is content in the tank. So whether that means he hosts something, or just kinda swims around and sleeps in the rocks, be happy with it.
Good Luck,
Mitch