Well the mounting plate is the esaiest most straightforward way....
here's how eightbit did itBasically you cut out the football shape to a tight fit and create some sort of support underneath to support the tball... Then cover the top with artwork/vinyl/contact paper (well look at the link w/picture instead of my rambling explanation)
I'd strongly recommend using a mounting plate if you want an "easy" way to do it... but there's some excellent pics of how others have done it sans mounting plate =)
good luck!
Rampy