I just finished several pieces for the Zentangles theme for our Postmark'd Art Group.
However, I kept one back to sell. The process I used was first to draw on a piece of watercolor paper, with ink, starting with the little Quail.
Then just added lines and designs, as I felt the need. To make it into a fabric postcard, I printed it on Jacquard's Extra Organza, and ironed it on my hand dyed fabric. Stitched some of the main lines and finished with a zigzagged edge of heavy black thread.