Answer1) Downloaded Minimum ADB tools , installed to C:\ADB for convenience2) Downloaded 4.6.1 stock image from http://fire-phone-updates.s3.amazona..._461013320.bin , saved it to C:\ADB and renamed this file update.bin3) Followed these steps to gain ADB USB access. Alternately, I found out later I could go to Settings on the phone, then to Device, then to "Get info about your Fire" and then tap on the Model Number several times until "Developer Options" comes up. Clicking that will take you to the option to enable "USB Debugging".4) I also grabbed the Kindle Fire ADB drivers from here for convenience in Step 7 (below)4) Rebooted into stock recovery by holding Power and Volume Up. Yes, you can do this from anywhere - phone on or off. And yes, you can still get to stock recovery this way even if you have Safestrap recovery installed5) Use volume down to reach "Apply update from ADB" option then press Power6) Open Command Prompt from Windows, reach your ADB folder (mine is C:\ADB in this example), type ADB devices. If you see what looks like a serial number (letters and numbers), then ADB is seeing your phone and you can skip to Step 8. If nothing there, follow Step 7.7) For me, ADB did not initially detect my phone. I ended up having to go into Control Panel in Windows, to Device Manager, find the Fire phone, choose Update Drivers, then Browse My Computer, Let Me Pick, Show All Devices, Have Disk, then find the folder from Step 4 (above) and add Android Composite ADB Interface by hand. Once I did that, I unplugged and replugged the USB to the phone and then typed "ADB devices" again at the ADB command prompt, like in Step 6. There it is! Ok, next step...8) Type the command ADB sideload update.bin and let the magic happen. When done, reboot the phone and everything is reset.9) If you're going to sell the phone, or if you don't want all of your Android apps from before repopulating (because some of them just aren't going to work or work correctly under Fire OS), immediately go to Settings/Device and "Factory reset your Fire" - this will wipe the SD partition where the old apps are saved.Cool side-note, regarding Step 9... I still had Nova launcher available. Running it under Fire OS works great! Nice to have the stability of the Fire OS the hardware desires, along with a zippy, traditional launcher to navigate.