How to prepare narrow window reveal for plastering

[Kirbs]

I'm preparing a room for a plasterer to come and re-skim, as whoever was here before us had done a poor skim coat over artex, which is badly blown.

This has mainly entailed chipping off the poorly adhered skim coat (not difficult, coming off in sheets due to how badly adhered it is), and then removing the artex using X-Tex remover (had it tested - no asbestos) ready for plasterer to come and do a proper job ready for re-decorating.

Problem is I've got to this window area, which is a single skin block wall (it's a dormer bungalow), where the reveal needs sorting out. I was thinking of boarding it (after foaming the gaps around the window a bit better) with moisture resistant board, ready for the plasterer to plaster over, but the reveal is so shallow that there's practically nothing to mechanically fix the plasterboard to underneath.

Would be grateful for any bright ideas? Thanks.

 

[Wayners]

I've stuck elements board on with foam. Plaster over.
Should use limelite plaster

That what I would do but I'm no expert at this