If you open the Installer.app package, you'll find a DMG in there. You can then partition your USB drive/internal hard drive/external hard drive with a 5 GB partition, and restore the DMG onto it via Disk Utility.

You boot from the partition, and after installation, delete it and extend your primary partition (if you partitioned your internal hard drive).

Apple EFI drivers suck. I've been trying to get windows installed on my MBP17" where I replaced the optical drive with a SSD and it's been pure pain.

You'll need the superdrive in particular most likely.