It really couldn't be simpler. here is how:
1. make a 9-patch
2. cut it in half lengthways and widthways to give 4 smaller blocks
3. arrange layout to suit!
I made mine with a limited palette, but it could be totally scrappy, scrappy but with the same colour in the centre of every block, using just 3 colours, etc.
This is a great block, with loads of potential, so just try it and have fun with it!