Which apps did you want to block? On which OS version?
If you want to block any apps that are part of the default OS install, you might run into restrictions imposed by
System Integrity Protection (SIP). If SIP is disabled, or you're running an OS without it, it's pretty easy.
One way to disable an app is to remove execute permission from the main executable inside the app bundle. If you do that, then the app can't run. You might get a failure dialog in Finder if you try to run it, or Finder might show a "slashed circle" imprint on the app's icon. It kinda depends on the OS version.
To restore the app, you re-enable execute permissions on the app's main executable.
If the app is owned by root (default for Apple-supplied apps), then you'll also need the 'sudo' command.
You can even put the removal of execute permissions into a Run Shell Script action in Automator, save the result as an app, and then use that app to disable other apps. You would then put the re-enabling of execute permissions into another Automator app, and you can drag and drop apps to enable/disable them.
The command-line tool that changes permissions is called 'chmod'. The name of the permission is 'x'. You probably want the 'a' attribute, so it applies to owner, group, and other mode-bits.
If you need specific details of the exact command-line, ask again and I'll go into it with a specific example. If you're already familiar with chmod, or can search for info on the web, then you should have enough to go on.
