Willowballs look like this to start:
And ours wound up looking like this:
This was much easier than making a moss pomander out of a Styrofoam ball. The willow balls were purchased at Pier 1 (I think) and then A. tied the bows on them. I hot glued moss all around, but it stuck really easily to the willow ball material and were good to go. The sheet moss covered pretty quickly - just keep your glue gun on low. Styrofoam balls are surprisingly expensive, and much harder to get the ribbon attached to, so I would recommend this approach for moss balls and possibly also for adding flowers to make pomanders.