I will be following the instruction on the Steam Support page regarding factory restore. I will note any issues I have with the instructions or if more clarification is required. I will be using Windows for these instructions. You can skip a factory restore if you have a new device or if you don’t want to wipe everything. I am just doing this for consistency.
In short download the image file from the Steam support page linked above in my case it was named “steamdeck-recovery-4.img.bz2” then download Rufus. Plug in a USB flash drive to your PC (Make sure its empty or it will be over written) Then run Rufus and click the select button and find the image file and make sure the Device has your USB drive selected. Mine was selected by default. Then click start. It took about 10 minutes to write to my USB flash drive. Then click close on Rufus. Then you can safely eject your USB drive from your PC.
Next make sure your Steam Deck is powered down then plug in your USB-C dock or hub and plug in your power adapter to it. Then plug in your USB drive with the image you just created. Hold down the Volume Down button and click the power button once you hear the chime let go of the volume down button. (Note I held the volume down button down until I saw the Deck logo and it worked so there is obviously a little wiggle room.) Once the boot manager opens up use the D-Pad to select the EFI USB Device and Press A. It will start reading the image file for about 2 minutes and the deck logo will show on the screen while its reading. It will then go to desktop mode. It appears this is just a live image of Steam OS. Once its fully loaded and you have touchpad control click the “Reimage Steam Deck” icon with the right trigger. It will pop up with a terminal and then a message asking if you are ok that it will destroy all data on the deck. Click Proceed if you want to continue. This process is really quick and only took about 5 minutes. Once its complete it will popup a notification that it is complete. Click Proceed. The Deck will reboot. You will then be greeted with the OOBE (Out of box experience) like a new Deck. Select your language, time zone, WIFI and login to Steam. (My mouse stopped working while going through the OOBE so I had to use the touch screen but keyboard still worked for entering the WIFI Password and Steam credentials.)This step is now complete.