UEFI shell on x399 for maintenance

Hey, I want to flash a raid card to IT mode, but am having simply the hardest time getting to a useful UEFI shell to run sas2flash.

I can make a freedos usb, and get the “couldn’t detect adapters because of PAL” or whatever it is when it needs UEFI mode to run the .efi instead of the .exe …
The option in the Bios to reboot into shell just errors out. It says it should copy the bootx64.efi to the root of a device, but doesn’t seem to work with a Fat32 USB.

Any suggestions?