Operating System not found when trying to boot from USB to install.

I followed this guide up to step 11. Unibeast said the operation was successful.

Now I am getting "operating system not found" error in every port when I try to boot to install. I chose legacy at step 7 and have legacy boot chosen in BIOS, as well as secure boot turned off.

That's about as far as I can figure things out based on google searches. Any help?