Good for orchids which really hate staying wet, or for landscaping in the tropics. The most important thing is securing the plant to whatever you want to grow it on. Common techniques involve tying the plant flush against the mount using fishing line, tight string, or even strips of old pantyhose! You want something which will not break down for at least 6 months to a year, giving the plant time to start anchoring itself with its roots. Wire can constrict the plant as it grows, so not ideal unless you want to remember to remove it. Small dabs of strong commercial glues, or low-temperature glue guns, are also good, and less conspicuous. However, check to see if the glue has toxicity warnings - if it is toxic to animals there’s a good chance it could be at least slightly toxic to the orchid. Mounts are generally plant-based: slabs of bark, sticks, pressed fern fiber, even timber (some folks say this should be non-pine though - we haven’t experimented enough to weigh-in on the subject).
For folks in the tropics a tree branch is the most common substrate, but large rocks or concrete walls are also used quite a bit. Unlike mounting on moveable objects, take some time to consider the long term conditions for a plant mounted in this location. How bright is the light, and is your plant already used to this level? (or does it need to be slowly adapted to it?) How hot or cold does this area get? Does it get regular rainfall in this location, or is it close to a hose? Is there decent airflow in this area, or do things quickly stagnate and rot there? Is it in the path of weedwhackers, destructive pets/kids, salt spray, etc.? And, perhaps most important: will you be able to easily enjoy seeing it there?
If you prefer to have your orchid indoors, potting is usually the best option. Take a look at our orchid potting article for inspiration!