Packing an fd file?

[blazini36]

Not sure if this is the right forum but I'm trying to figure out what is required to create an fd file. I'm not familiar with Insyde software, but there are several open source tools to unpack an fd. I used one and it produced 4 files, platform.ini, certificate.bin, isflash.efi, and the 16mb Bios.bin. I modified the bios with a script. I can flash that EEPROM chip directly with a hardware programmer but I'm fairly certain that the software flasher (uses h20fft) will only work with the fd file, I can't find any info about how to create an fd file so I assume it's a proprietary software tool. This is a signed bios but others have been able to create the fd file that works with the software flasher, but nobody talks about how it's done. Any info on this?