It has been a while, but I had to wait for my entry door to be fabricated.
So here are some more pics of where things are at now.
There seems to be some variation of thickness of the hearth bricks. Not much, but up to 2 mm, so will have to try and level it all when I set the hearth bricks on the perlcrete.
They also have a bit of a sharp edge/lip, so I"ll sand the edges, so that they are a bit smoother.