Looking to build up a the top of a fireplace hearth \~3/4 of an inch. to level new tile with the firebox. I was thinking of using a heat approved 1/2" or 3/4" cement board after leveling and bonding it to the cinderblocks and bricks with some type of mortar as well as level the base and fill in voids at the same time. Then tiling on that. Will almost certainly be less jank and more level than if I tried to build up 3/4" of mortar myself. Anyone done something similar?