One recipe I have goes this way: a mixture of half inch stone chips, gritty sand (sharp), and peat, with a surface of stones to facilitate spreading. I suspect the presence of silt, too.

Needs to be grown in the open with no shading or drips.

Helps if you keep them away from plants that ping! seeds, unless you love fine weeding.

They often grow in scree, in areas with low rainfall (11"+). However, they also experience snowfall, low cloud, and sharp southerly winds over winter/spring.

If you're growing it in a container-deep as well as wide is probably a good answer.