OK I have done stone on cement walls and block walls using spec mix but Now I am putting stone around a Direct vent gas fireplace and flagstone as a hearth.

I am installing a natural gas direct bent unit model Ventana by Valor Fireplace.http://www.valorfireplaces.com/products/index.php?page=386

I have built a hearth base out of 2x6" and 3/4" plywood. I am using 2 1/4" thick red flagstone as a hearth. I will be cutting this and chip facing the front edge. I will make it in 2-3 chunks. Each about 100 #'s Do I just set it on about 1/2" of specmix right on the plywood and level?

Then around and above the fireplace and below the hearth I will be using a natural East Desert stone strip about 2" thick I was thinking of just screwing on some expanded metal lathe and then using specmix and wiring up pieces as I go and cutting off the wires later. I can do it over many days and thus will only have to go up a few stones at a time until they set. The first row of stones above the hearth will sit on it but under the hearth I was planning on leaving them raised 1/2" above the floor for the carpet to tuck under.

How do I prep the 3/4" plywood hearth base? anything?

The vertical surface is 1/2" plywood over framing which is almost solid on the front face but the fireplace comes with this 1/2" cement board around the perimeter and a very large chunk over the top. these areas are not well supported?? I have some rather long stones that will span the top and will rest on the side stones and should support my stones above the fireplace opening so I only need it to adhere to the cement board? Do I need to put tar paper on the wood prior to lathe?

any help and or links would be appreciated.