turning bios software into an img

a new bios version for a notebook contains of a bunch of folders and files. In order to flash the new
bios version onto the notebook, the folders and files have to be turned into
an img that can get burned onto an usb memory stick. That stick will then connected
to the notebook get booted and the new bios version will then get flashed
onto the notebook. I tried creating the img with gnome disk utility. An img got made. No errors. But
after burning the img onto an usb memory stick the stick would not boot. It did not work.
I have been told I should use a piece of software called Active@ Windows PE Boot Disk. It does
not sound as a piece of free software. And therefore I do not want to use it.
Do you know how I can turn the bios made up of folders and files into an img usable for
flashing the new bios version onto the notebook? Thanks.