Google has changed the way you can create a recovery image. You used to be able to open the chrome browser and type chrome://imageburner and follow the onscreen instructions, but now that command is no longer an option. Google has now created their own app called the "Chromebook Recovery Tool". You can search for this app in the chromebook webstore or visit the link below.
Chromebook Recovery Tool App:
If you would like a walkthrough on how to download the chromebook recovery utility and create a USB recovery image, click the link below to watch the video.
Chromebook Recovery Tool Walkthrough video:
You will need:
a working chromebook
at least a 4GB USB flash drive
model number of the chromebook that you need an image of - example would be WOLF C4A-A2B-A7R. You can find the model number on the recovery screen (a.k.a yellow exclamation mark screen). You can get to the recovery screen by the following keyboard commands (esc + refresh + power).