How to fill in hinge and door handle mortises?

Question

Replaced an interior hollow core hinge door with a bi-folding one and now need to fill in the mortises in jambs.

I've read people recommending all sorts of things and got a bit confused. There's Bondo, there're all kinds of putties, spackling etc.

Is there an easy (and preferably cheap) solution to fill those in? The door is white, so would be great not having to paint the filling afterwards if possible.

Answer 1

I'd put in a piece of matched wood, then use an appropriate filler to smooth the junction between the patch and the frame.

If it's painted, you can get away with other materials.