I'd suggest to mount it directly (bare) to whatever you're going to mount it on, then add a little sphagnum over the roots to help it stay hydrated while it is growing new ones. I have found that when there is moss between the plant and the mount, roots grow into the sphagnum instead of grabbing the mount. By putting it on top of the roots, they still get the benefit of it while being encouraged to grow onto the mount.