in this post , i have explained about downgrading into Catalina from Monterey.
Process for downgrading from Ventura to Monterey is similar pattern,
just use Monterey link in "How to download macOS" page (to download Monterey's last stable installer, which is 12.6.2 at this moment) instead of downloading Catalina's last stable installer file,
OR, use Monterey's version 12.6.1 installer for now by using command-line in Terminal, as that is less buggy, at this point of time.
So, cmd line will be:
$ sudo softwareupdate --fetch-full-installer --full-installer-version 12.6.1
Then find & extract the "InstallESD.DMG" file, from downloaded installer file. (Right click on downloaded APP file, & select "Show Package Contents),
then you can create ISO file.
$ hdiutil makehybrid -iso -joliet -o Monterey-installer.ISO InstallESD.DMG
Then please follow other instructions, in that linked page.