Mounting a piece of Mediocalcar decoratum

[rbarata]

My plant is growing a lot and fast in a plastic pot with sphagnum. I would like to mount a piece of it, just a branch, in a slab of cork.
What do you think that would be the best way to do it? With a sphagnum layer only?
And is there a best time to do it...that would be probably now that it is growing.

Opinions please....thank you!