I have a small Carex that usually grows on river beds, in shingle-gritty sand. It forms mats, dies back in winter, leaving the remains on the surface to protect the growing points. I suspect if of being like Parahebe: growing on the downside of rocks in a shingle swirl where it can withstand flooding.

I'm wanting to put together a planting medium that imitates but doesn't replicate that habitat. To be used in a large plastic planting baggie.

Hoping for advice on the layering and the planting medium. (In the habitat it is unlikely to be peaty: more likely to be a clay silt.) And a watering arrangement for something that would be able to access moisture quite readily even in summer in a natural habitat.

As far as I know it is not a scree plant as such.