Using a printers template

[m5heath]

I regularly create covers for Print on Demand Amazon books. The way this works is that a template is acquired from Ingramspark (see the attached jpg image) as a pdf document. I have been using Photoshop which works reasonably well. Having opened the pdf, I create a marquee around the coloured part - which is the actual cover template - and then trim away the white surround. But it occurs to me that the process might be more efficient with InDesign. 

The question therefore is: how do I achieve a cropped template in my ID desktop to start creating new layers with images and text etc? I need to save the completed cover as a png or jpg for Amazon. I am told that I can't crop out part of a page in ID but is that right? Can't understand why that isn't an option. Maybe I have to crop in PHOTOSHOP and then open in ID?

Any advice gratefully received.

[James Gifford—NitroPress]

All this. You can get to what seems like a proper result in several different ways. But you can only get to a fully confirming, accepted cover layout for a service as demanding as KDP or Ingram by following a fairly narrow path — especially if you have to make any changes or adjustments when your first submission is rejected for cryptic reasons.