There is no need for inside cleats or backing. Here in the US, we call frame-less cabinetry "European" style. Nothing more than 2 sides, top, bottom and back. While a rack or multiple racks will have to support much more weight, like Rob (or someone) previously said, the weight is all bearing straight down on the sides. The top, bottom and back only hold the sides together.
I did use face frames on my racks but only because I prefer that look to frame-less. At the time, I had a very nice Castle TSM35
pocket hole machine. All the holes and screws are visible only on the inside. For a one off type application, Kreg makes a nifty little jig that will work just fine to hide the fasteners. Easily found at any of the big box home improvement stores.
Something like this.
They have many other versions to offer but this will be fine. http://www.kregtool.com/Pocket-Hole-Jigs-Prodlist.html