Nothing in our house is level.

This goes for the hearth as well.  

Of course.

When we ripped up the stamped concrete, we found another layer of concrete underneath.  We need to build up this recessed area so when we lay the tiles (which match the kitchen floor) they are level and flush with the base of the firebox.  To do this, we will stack layers of plywood, on top of which will go the wonderboard, and then the tile.  But we can't do any of that until we create a level base for the plywood.

We were originally going to use self-leveling underlayment, but after doing some research we figured out we could just use some mortar.  So we layed some into the "deep" sections and tried to level it off the best we could.

Now our hearth looks like this:

We put the mortar base down last night, and we can't do anything until it dries.

So now we wait.