For Fireplace Stone Hearths that will lay on a surface that is not perfectly flat / level or if you simply need to raise your hearth by one-half inch, we suggest that you use our CV230 Micore 300 Board, a lightweight and dense fiber board that can 'cushion' between the bottom of your stone hearth and any uneven surface.  Micore board measures 20 x 72 x 1/2" and can be easily cut with a utility knife, if needed.  If ordered without stone facing, this board will by cut into three or four pieces (for packaging purposes) which can be laid edge-to-edge when installed. MSDS

You will likely need to use our construction adhesive for natural stone and masonry products:  adhesive F26, designed for use with masonry products so it won't bleed through the stone.