Secret fixing external door frame?

[Kes]

We're having a new external door and frame made in idigbo which we are intending to give a natural finish in tung oil. We don't really want to see the fixing screws for the frame showing (I know they'll be in the door rebate). The door is being fitted by a carpenter but one never knows how neat he will or can be, and once a hole is drilled in the wood it's there forever.

Is there a way of secretly fixing a door frame? I had thought of 4" square plates screwed to the outside of the frame with 2" overlap on the inside, and the plates being screwed to the wall and then plastered over. Would this be sufficiently firm? Would filling any gap around the frame with squirty foam help - is there a structural squirty foam that is stronger? Or is it just big recessed screws and coloured filler?

 

[^woody^]

Use a plug cutter to cut some plugs from the back of the frame timber, then recess the fixings and insert the plug.

You should be able to match the grain, sand and then decorate to make virtually invisible

Door frames really want to be fixed through the frame to avoid things like twisting or being levered off by burglars.