after acquiring a KFHD 7 Demo from Ebay, i used the following procedure to install a stock ROM using a Linux desktop.
requires factory cable, android-tools.rpm, and KFHD SRT download.
to get fastboot binary you need to install android-tools from the EPEL software repository, for details see https://fedoraproject.org/wiki/EPEL
open a terminal command line window on the Linux desktop. $ is the bash prompt and shouldn't be entered as part of the command.
$ sudo yum install android-tools
unzip KFHD SRT you downloaded.
$ unzip Downloads/KFHD_SRTv1.3.5.zip
before connecting the Kindle, enter the following command.
$ fastboot -i 0x1949 getvar product
should show < waiting for device>
now connect a factory cable from the Kindle to the desktop, and power on the Kindle. It should show the Fastboot screen.
the terminal bash window should show ROM version of the Kindle:
now enter the following commands in the terminal bash window.
$ fastboot -i 0x1949 erase cache
$ fastboot -i 0x1949 erase userdata
$ fastboot -i 0x1949 flash recovery images/recovery.img
$ fastboot -i 0x1949 flash boot images/boot.img
for Restore-Factory Rooted with SuperSU.apk, enter this command.
$ fastboot -i 0x1949 flash system images/system.img
or for Restore-Factory Rooted with SuperSU.apk, Apex Launcher, and PlayStore, enter this command.
$ fastboot -i 0x1949 flash system images/system2.img
fastboot -i 0x1949 reboot
disconnect the Kindle and it may need a couple of reboots for the stock ROM to come up.
now that was simple. i hope this helps.