I've done this before. I waterproofed the area using Kerdi board and tape. Fixed split face white quartz and I back buttered each piece to make sure all gaps were filled, then each piece was laid almost like a brick - I pointed a touch of adhesive onto the edges of the piece before - again, trying to leave no gaps open. I know water can/will soak through to the kerdi but then finished off by absolutely soaking the lot in impregnating sealer.
Job looked great and my customer seemed happy to make even more work for her cleaner!
I warned her that I would be making a mould-garden but she wanted to risk it.