" Do I splice the white wires together, the black wires together, and then add pigtails to the white and black wires and connect the pigtails to each of the outlets (and leave the red wires pigtailed together)?" That's exactly what you do.

You want the cut outs in the granite made in the shop on the CNC machine or with a water jet. Jimmy and his grinder on site are going to have to make the stone significantly weaker to get a nice square. You don't want "square" square either. A bit oversized with radii in the corners is much stronger, like the bit on a CNC machine would make. I broke a backsplash while removing it because of the over-cutting that was done by hand to make the duplex receptacle hole. Fortunately this stone was quite forgiving.

oldalgebra- Your wooden box should work fine as a facade, but, to be to code, all the connections must be inside a proper electrical box, and that electrical box should have a cover on it. That means that you should leave a bit of length to the lamp cords as they need to go into the electrical ceiling box so they can be clamped, and code requires that all wire ends being connected need to protrude from the open electrical box by 6" while they are being worked on. If the ceiling box is already in place in the ceiling, I suspect that the electrician may install an extension ring to accommodate all the wires legally, and use a cover with a hole and cable clamp in it. In addition, the electrician needs room to work with the wooden box not in the way, so additional slack in the fixture cords is also necessary for that purpose. I'd install a couple of long screw eyes in the ceiling and into a joist and then hang the wooden box temporarily from these so that someone doesn't have to try to hold the box up while someone else does the electrical. If it were me, I'd have about an extra 2' of lamp cord for each of those fixtures to make it easier to do the electrical properly. By the way, how do you intend to securely fix the wooden box to the ceiling?

We need to install two outlets in our beautiful granite island (by code) with waterfall elements on each end. Our tile and stone company suggested against using pop-up outlets with stone covers. S-box makes the only nice looking product I could find. Does anyone have experience with these? Have they been reliable?