I tried using that guide before but it failed on me big time. The guide over there only lets you install Windows in an emulated BIOS environment and not in a UEFI environment.
So after some experimenting, I came up with my current method which works via UEFI really well. At the boot selection screen, only EFI Boot will show up. A native UEFI installation is always preferable.
Here goes. It's easier and does not use imagex. Rather, it uses the built-in dism.exe utility.
Connect external drive to Windows VM. You must have a Windows VM in VMware/Parallels/VBox, or a Windows PC. Any existing Windows environment will do.
What you need:
install.wim file (obtain this from your Windows ISO)
Open elevated cmd.exe (run as admin)
Note: All commands aren't case sensitive, including pathway to files.
Type diskpart
Type list disk
Take note of the disk you want to select
Type select disk 1 (if your disk is Disk 1)
Type clean
Type convert gpt
Type create partition EFI size=100
Type format quick fs=fat32 label=EFI
Type assign letter=S
Type create partition primary
Type format fs=ntfs quick label=W2G (or any other name you wish for label)
Type assign letter=E
Type exit
Open up File Explorer. In your C drive, create a new folder named WIN2GO.
Put the install.wim file in this folder
Back in cmd.exe:
Type dism /apply-image /imagefile:C:\WIN2GO\install.wim /index:1 /applydir:E:\ (this process will take quite a while)
Type E:\Windows\System32\bcdboot E:\Windows /s S: /f UEFI
Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot.
Proceed installation normally.
After installation, install Boot Camp drivers. Feel free to trash the VM once you're done too.
For best results, use USB 3/Thunderbolt. If you don't have USB 3, use Thunderbolt. If you have neither, stick back to the internal drive
