You're doing somehing different than what I proposed. Let me do it in steps to try to be more clear:
- Under the live view, click the placement button and choose "Template/centered"
- Add your image(s) at your 594 x 420 size with crop OFF
Now when you are in Template/centered
placement mode which is a special placement mode, your crop marks will be on the red outline(s) and not the print itself.
P.S. This has nothing to do with layouts or the [Template] thumbnail. Here you are using the Template/centered placement method.
Regards,
Mike