Why the flat side of a cinder block? I read this to mean the holes will be horizontal? Are you looking for ventilation? The traditional method is with the holes vertical topped with a wooden sill. However you do it you need to get the cinder blocks level. That stops vermin or other critters from using the holes as a route inside and you can manage ventilation other ways. I think the holes running horizontal just gives vermin an opportunity. I'm thinking of snakes as much as anything else. Keep it simple. Besides, the bedding inside the coop floor will block the holes so no ventilation benefit if they are horizontal.
Attach your apron wire to the wooden sill and run it vertical to the ground, then bend it 90 degrees and go out maybe 18". You don't have to bury it but I like to remove the turf, say 2" deep, and put that turf back on top. It's very effective against digging critters and is out of the way of weed eaters and lawn mowers. You can hold it down with lumber, blocks, or rocks until grass grows through it and holds it down but I've had some issues with the apron wanting to curl up enough to catch a weed eater when I did that inside a dog pen to keep the dogs in.
My coop has a dirt floor. When I built it I hauled in enough clay dirt to raise the floor level 2" to 3" to keep water out. I don't know your topography but if rainwater run-off runs toward your coop you might want to consider that. I also put a gentle berm and swale on the uphill side of the coop and run to keep rainwater run-off away.
