Need to attach a mantel to stone hearth

Another recent thread about attaching a box beam hearth to a stone fireplace got me to thinking about an upcoming project. I will be building a mantel out of some salvaged american chestnut. the top of the mantel itself will be made out of relatively thin (3/4 to 1") stock, but a 3-4' piece will be mitered onto the front and side edges of this, dropping down over the edge of the stone and thus giving the mantel a much thicker, more massive look.

My question is this, the top of the stone is of course, not level. Any advice from the experts on how to approach this? My present idea is to tap-con some backer boards to the stone, then affixing the mantel to these (probably via adhesive, as I don't want any nail holes or other blemishes in the top). These boards would have to be shimmed or scribed in order to achieve level. FYI, I believe this is a real stone fireplace, not just stone veneer. Thanks...Jon

jon, i`d use builders shims-n-glue to give some level wooden glue blocks, since you plan on a 3-4"skirt it should be no problem to level any inconsistancies. in fact looking at the photo it`s possible that a piece of baltic could be set in construction adhesive and left to dry, it dosen`t appear to be out of level much? .02 tod

There are many ways to approach this.

You could skim coat the top with mortar and use a board to get the mortar level side to side and front to back. You could simply apply four or dollops of mortar on the corners and a couple in the middle and do the same thing.

You can bed the mantel in mortar, simply screw some hangar strap to the underside and bed the mantel in a nice thick layer of mortar.

You could get a heat rated RTF silicone and bed the mantle in that.

If the ends of the mantel are to be over studs you can pocket drill & screw the ends of the mantel to the wall after bedding ir for security then cap it with your nosing.

You could extend the mantel a bit to reach studs and use wood support brackets.

The list is endless. I'd say let the structure behind the sheetrock have a voice in your method and design.