I have pieced mine, again in antique colours, ready for embellishment. Postcards need to be 6"x4" finished size, so I have made up a foundation of 7"x5", then have marked and machinestitched the 6"x4" outline to be embroidered.
I pieced on a foundation of muslin, with iron-on pellon underneath. This will be what I work the embroidery on.
To put the postcard together, I will then place a piece of strong stiffened vilene or buckram(or both), with the backing of muslin (with printed postcard design) vsioflexed and ironed to the out side of the vilene.
This sandwich of fabrics will be restitched again just outside the original 6"x4" line of stitching.
After trimming the postcard to the machined line, I will satin stitch the outside edge, to finish.