@bricktop135 Though George is right about the USB key setup to boot Macs (and other machines) this is not the perfect way since it has issues.
Depending on the Mac you have you should be able to boot iPXE directly from a USB key (slightly different to what George posted). From what I read between the lines you have PXE settings in your DHCP server already or you wouldn’t have been able to PXE boot the windows PCs for imaging. Or did you use George’s USB key manual for the windows clients as well?
So back to the “other” USB key method. Simply format a USB key with FAT32 and create directories \EFI\Boot\ on it. Then copy ipxe.efi (found in /tftpboot on your FOG server) into that sub-directory on the USB key and name it bootx64.efi. So you end up with a single file on that USB key: \EFI\Boot\bootx64.efi
Plug in the USB key, fire up your Mac and hold down ALT on the keyboard. You should see several boot entries. Select the orange one called “EFIBoot” and see if you get to the FOG menu.
Please take a picture in case you hit an error and post here so we can have a look.