- Download the installer from the App Store
- Goto Applications & right Click on Install OSX…. , select view Package Contents
- Under Shared support select InstallESD.dmg, hold the option key & drag it to the desktop (this will make a copy)
- use disk utility to format an 8GB USB stick as 1 partition, Mac OX Extended (Journaled) with a GUID Partition table.
- Then restore InstallESD.dmg to the stick.