The groove in the concrete needs to be deep enough to make a thick enough patch over the conduit (at thr thinnest spot in the patch) to not crack ad look bad. That is about it. You need concrete tight connectors for all conduit and conduit to box joints, and a type of conduit rated for direct use in concrete. It is a nasty dusty hand job for the most part. Scoring more than just two grooves can go a long way towards preventing going through the slab all the way when breaking out the groove material. There are advantages two, three, or more grooves. You can ten use a chisel driven in a groove to break off a section of concrete with the next groove as clearance. If the spacing between the grooves is smaller it is more likely to break off near the bottom of the grooves.

When I had the island removed from my kitchen to restore the original heartpine floor I also had my floor guy leave the wiring and he installed a heavy duty brass 2 gang outlet with heavy covers. He found it at an electrical store for industrial stuff. I have had it in use for about 6-7 years...even before my kitchen redo 4 1/2 yrs ago. I have a movable work table and I keep my Cuisinart plugged into the one side with the appliance sitting on the lower shelf 24/7. I do mop the floor ( John I can come and do yours too if you like :) ) but have never used so much water that it was a concern, would have to really flood it and then worse problems would ensue. I got down and looked inside the closed door on the 2nd outlet side and there is not even any dust....door fits flat and tight. There was a small amount of crumbs in the other when I removed the plug and I used a slightly damp cloth to dust them out. All done and clean and safe. There was no mention of code violation when the new kitchen was inspected and the guy was looking at every little thing. Due to the distance form the sink/water supply it isn't a GFCI . I am glad I have it and there is no risk at all of tripping since it is slightly under the work table and if the table is out of the kitchen the doors are completely flush to the floor. John you will love it...go for it. see it at the far left of pic near bottom: in use , you can see where the sink is in relation to the table/processor:

Are you planning hardware that protrudes? I think part of the reason for counter overhang is so the counter protrudes the same or a little more than hardware. Also, drips over the counter edge tend to land on the floor rather than down all your drawer fronts. this info is all just FYI. It's my cautionary tale. At least you are making an informed choice. I have kicked myself over and over for not catching the aisle width oversight on my own drawings. I didn't realize the error until it was too late and too costly to move a wall with gas and electric in it.. I have a counter depth fridge, but with the thickness of the fridge door, the fridge handles and the counter/hardware on the opposite side of the aisle, there's only 32 inches left in front of my fridge.

At the last house that we had built, I knew that I was going to float the couch in the living room. I spent some time at the site measuring and remeasuring, so I could have the floor plug under the couch (more toward the back of it). This worked great, since I placed a narrow table with a lamp behind the couch. If you know the furniture layout, then it should be fairly easy to measure it out and make the determination.