First consideration is that you're dealing with a natural stone tile and you should first ensure that your floor structure and subflooring are adequate for the application. While ceramic tile installations over wood framed floors require a deflection in both joists and subfloor of L/360 or less, natural stone requires L/720 or less, a far, far more rigid floor.
And natural stone tile requires a double layer of plywood or OSB subflooring regardless the joist spacing.
That's the first thing you need to be checking and correcting.
Over that subflooring you can add a CBU (your Durock) or other tiling membrane and tile. Read and follow the manufacturer's installation instructions for whatever tiling substrate you choose.
Second major consideration, and one you'll want to incorporate in your subflooring upgrade, is that your floor must be very, very flat to accommodate those large format tiles.
The tile industry standard for substrate flatness for tiles that size requires no deviation from intended plane of more than 1/8th" in any 10 feet and no more than 1/16" in any two feet. That is an extraordinarily flat floor and you're gonna find that you'd really like yours to be better than that.
I would strongly recommend you also invest in a mechanical tile flattening system to aid you in setting those tile without excessive lippage. There area a number of such systems on the market. Two that spring to mind and with which we (TYW in general) have a good deal of experience are the TLS
and the MLT
, each of which have a great deal of feedback here on the forums.
Those big stones are not for sissies.
My opinion; worth price charged.