Sorry, I think I am not being descriptive enough. I do want the electronics on the back of the leather (although you are making me think; I wonder if leather would be a good thru-hole mounting surface for a paper-duino like thing). Anyway, I think that your idea to use an awl or leather punch to cut a tiny hole is a good one. Now you said "and then mount the LEDs like you would any other fabric". To me that means sewing conductive thread through the leather, which I'd rather not do... maybe you mount to fabric differently?