Silk, can you put a zipper at the edge of the pillow, at one of the seams? At this point, that's what I'd do. Put the two pieces right sides together & sew around 3 sides of the pillow; then, add a zipper on the fourth side.
If it seems too plain, what about adding some piping? Or you could add some faux binding -- just cut your binding strips to be 1.5" (3.8cm), fold in half & attach to each of the quilted pieces before constructing the pillow. Then, sew the pieces together with a 1/2" (1.2cm) seam allowance & you'll still have a 1/4" (0.6cm) faux binding showing on either side of your pillow. I'd do an invisible zipper to all you see is clean edges.