If you give up on the mounting, I grow mine in a small 2in net basket just like the pic. That basket is set into a larger clay pot filled with irregular fired clay pebbles (not hydroton). The clay soaks up a lot of the heat so they can enjoy the sun.
If I were you and wanted to continue to grow these I would find a better source of this plant.
Your plant should like this when you get them.

good luck and I suggest
Tolumnia Orchids (Equitant Oncidiums): Orchids By Hausermann