When you say "clone", do you mean pin-equivalent or just another SoC-based board with similar features and performance?
If you're trying to duplicate the RPi exactly, you won't be able to. Nobody else can get the BCM2835 chip except the RPi guys.
If you're trying to duplicate the RPi exactly, you won't be able to. Nobody else can get the BCM2835 chip except the RPi guys.