How to fix this hole in the easiest way?

[Leaff]

Going to install a fresh intellivent in the duct.
My plan is to glue a cut piece of renovation plasterboard edge to edge, paper tape, and spackle.
And a piece of OSB behind the plasterboard so the fan screw has something to grip onto.

Possibly filling out with some foam sealant as well.

It should be faster and easier than filling out with cement, etc. Unless someone else has a better idea?

 

[Ossian K Olsson]

Going to install a fresh intellivent in the duct.
My plan is to glue a cut piece of renovation plasterboard edge to edge, paper tape, and fill.
And a piece of OSB behind the plasterboard for the fan screw to have something to grip.

Possibly fill out with some foam as well.

That should be faster and easier than filling out with mortar, etc. Unless someone else has a better idea?

I would use joint compound!

 

[Leaff]

I would have used gypsum filler!

Does it adhere well to mortar and plaster?

Shouldn't cement-based "husfix" be better then?