Please provide the image you are referring to. I need to see the image of the wall detail to determine if it could accommodate a recessed receptacle box and what the mineral wool reference implies about its construction.Without the image, I can offer some general principles: Wall Thickness

The wall needs to be thick enough to house the depth of a standard receptacle box. This is usually 3.5" for a 2x4 framed wall.

Stud Cavity

A receptacle box is typically installed between wall studs. So, the detail needs to show the framing (studs).

Mineral Wool

If mineral wool is being used as insulation, it indicates the wall is likely framed with studs, as the insulation is placed between them.

Sheathing: If there is sheathing in the exterior or interior, then you must consider the thickness of that too, as well as how the box can be attached to the framing through it.With the image, I can give you a more specific and accurate answer. Flag for review