The motherboard has only (1) M.2 slot, as with any motherboard. If you want to go this route I recommend waiting for the 960 EVO or 960 Pro's with larger capacities coming out from Samsung. All should be widely available by mid January, and some sizes are available now.
Keep in mind that the exact specs are: M.2 NvMe 2280 3.0 x4 PCIe (You can only use 2280, unlike many ROG dedicated boards that have attachment points for other sizes)
