Hi! Yes, I was typing by hand, not using the .bat file. So far as I know, batch files run on Windows. I'm running linux on the Raspberry Pi and don't know enough about it to run that way, so just used the bat file as a reference for all the correct fastboot instructions.
The instruction for flashing the system is pretty simple. Basically "fastboot blahblah flash system foldername\imagename.img"
There's not much choice about where it goes, just "system". Maybe you know more about it, if there's a different name than what's used in the tool.
I flashed the other files to their locations without issue. But they weren't 1.1GB like the system file is.
Apologies for the late reply, but try adding -S 256M in between the "flash" and "system" in that command. That should force fastboot to flash the image in parts.