8.) [10.5] Prepare the USB-Stick

Put your USB-Stick in any MAC you have and start Disk Utility (Application -> Utilities -> Disk Utility).

1. Start Diskutil
2. Select the USB-Stick itself as show in the foto (do not select a partition on the stick).
3. Select Partition
4. Under Volume Scheme select 1 Partition
5. Click "Options" and in the Options sheet select "GUID Partition Scheme"
6. Choose a Name without spaces (I used EFIBOOT)
7. Click "Apply"
8. DONE (it should look like in the foto)