Here is how I grow Orchids on Saucers.
First of all, clay saucers are better than plastic ones. They dry quickly, they are more stable and it's easier for watering (I put them in a bath for 2 to 15 minutes if the moss is very dry).
Usually, I drill 4 or 5 holes (4 for the bonds - 1 also used for fixation- or 1 more for the fixation) depending on my mood. You just have to put a little water in the saucer, to use a tile drill and to be careful and gentle. Good luck if you try !
For mounting, I put a layer of sphagnum (like a dome) in the bottom of the saucer, then the plant which is attached with bonds. Finally, I press wet sphagnum over the roots and... miracle... the sphagnum doesn't fall out ! Then, the roots develop and fix the mounting. Sometimes, when the sphagnum is too dry, some pieces may fall out.
This photo showed is my first saucer (cracked !). Now, I'm a pro !
Here are some photo of orchids in saucers. It's possible to grow large Phals, such as hieroglyphica or lueddemanniana, but also Brassavola, Cattleya, Dendrobium... I really like saucers, the look of the orchid is very natural.
Brassavola perrinii (in a saucer since 3 years)
The same flowering this summer :
Step by step with a saucer "ready to use" :
All you need, very simple, almost nothing ! NZ AAA sphagnum is the best, you know that.
And here it is