They are mounted directly on the driftwood.
When they are not on display, they are grown inside the greenhouse where the misters keep the humidity around 50%.
During the winter, I turn off the misters and just water as needed.
When they are on display inside the house, I take them outside every morning and water them down with the garden hose. Once the wood has dried up a bit I take them back inside.
Here are some old posts with pictures of these two orchids and some more when they were initially attached to the driftwood.
I thought I posted a tutorial on how to create orchid mounts here but I cant find it. I might have posted it on another forum (Bad John! Bad!!! hehehe).
I'll see if I can locate my reference pictures and I'll work on a how-to and add it to the articles.