Get a piece of wood at wide as you need and then using smaller blocks wrap it around the existing mantle on the sides to secure it. You could have some screws come from underneath that would be hidden from direct view or make something that would compress into the existing mantel. Paint it all white and then secure the TV to this piece somehow, such as mount like someone proposed. It would be completely removeable. Update: just to add, as mentioned in the comments you could also just use a few small C-clamps where the arrows are to secure for a real quick and simple solution. Hide the clamps with pictures, plants, etc. Answer from schirmyver on reddit.com