I'd use a gun applied cartridge adhesive, a flexible one would probably be best for this, rather than tile adhesive. If you can lay it flat while the adhesive sets all the better, if not use tile spacers and leave them in at least 24 hours.

Something like stixall or Sticks like, if it's water based I would lightly dampen the surfaces first as they are likely to be very dry and suck the moisture out of the adhesive. I wouldn't use Gripfill as it's a bit thicker and may stop the tile setting back flush with the other tiles. You won't need to use a vast amount, just a few dabs, otherwise it will make the tile stand proud of the rest.