The mod can be done with MMtool or UEFItool, on a full dump made with Intel FPT tool, on the CAP file from Asus or in the “Intel Image”, saved as ROM, extracted with UEFI tool.
This board has no USB BFB feature so, the traditional flash methods will not work due to the Asus/AMI security features using modified bios files, expected.
Depending on the file chosen to mod, CAP or ROM there will be different tools and routes to follow, so read the fowling thread…that it’s also linked in the guide you followed
Guide for ASUS mainboards
with an AMI UEFI BIOS
1 NOT POSSIBLE on this board
2 AFUWIN with /GAN
3 AISuite
4 Flashrom