I made them by finding heatproof objects to flip upside down so I could drape the felt into bowl shapes. This one was shaped over the bottom of my metal car mug. To hold the bowl shapes in place, I wrapped and tied them with some cord, then zapped them with the heat.
This is an object lesson in attending workshops. Often you learn something that gives you lots of fun for a day or two, but disappears from the radar screen as soon as you get home.
And that's fine. Sometimes a workshop is just a little vacation; you don't always have to learn something that changes your life. But it's always nice if you can make something good enough to keep -- or give away.