Creating a EFI partition
Usually EFI is on your Macintosh HD. It's likely still there, but not used due to messed up settings. This very easy to fix:


Boot into a Recovery partition, DVD, or USB drive. Using the installation media that came with your device will suffice.
Once loaded, you'll be presented an interface like:





Close this window, and you'll be prompted to choose between Startup disk, Cancel, and Restart.
Select Startup Disk. The mere act of opening this utility with run the appropriate bless command in the background, repairing your EFI setup.
Select Macintosh HD
Restart
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