I forgot to mention that I want the postcard to be at least 5X7 inches. It is a mailer, so it needs to designed with that in mind.

The size of the postcard should actually be dictated by the artwork. Please do not adjust the aspect ratio of the artwork.

Hi project owner,
you mention that the postcard will include a front and back side and in comment section you said it's a mailer !!
i'm confused !

The front side is the artwork. The back side is text and graphics on the left half and blank on the right half to leave space for the mailing address and stamp.