Hello, I'm trying to replace the ceramic tile in front of my fireplace insert. I used a hammer and chisel to remove the old tile, and the result left an uneven concrete slab to lay the new tile on. Now, I am left having to find a way to fill in a few spots where the concrete chipped along the corners, and then I need to even out the base to where it's flat enough to lay the tile. My problem is that I can't raise the base by much, as the space between the base and the bottom of the insert is less than an inch, and the new tile is about 1/2 inch thick. Is there a mortar that could be spread on and not raise the floor more than a quarter of an inch, while evening out some of the bumps left from lifting the old tiles?