Which Chrome OS did you download in https://cros-updates-serving.appspot.com/? I assume any common? Doesn’t matter what the size is? I choose the v84 version.
it is mentioned in the article which one to download
After that, download the official Chrome OS recovery image from here. Open the website and search for “rammus”. Now, click on the latest recovery image (right now it’s 80, but it may change in the future)