It's not essential for a clown's health to host in an anemone, nor is it essential for the anemone (in our tanks - can be very different in the wild). Many clowns available now are captive bred and have never seen an anemone!
I recently added a 10 year old ocellaris to my tank, given to me by a friend; the clown had never seen an anemone in her life. That clown is happily hosting in a Kenya tree coral (following a brief affair with some Xenia) and completely ignores 5 RBTAs on the other side of the tank. Your clowns may eventually decide to host in an anemone, but they may not. While I can understand you wanting to see the clown and anemone interact (I wish mine would), sometimes it just doesn't happen.