The instructions on pillow package read that for a pillow 12 x 12 I'll need a cut fabric square size 13 x 13. It just seems it would need more room, though when I did as you suggested it looked darn near right on. I'm making a pocket type pillow so I can wash it. If I sew the final seams 2-inch down the sides before the flap, the pillow should sit snug within the outer cover. I figure that I can pin it, just to be sure, before sewing.
Is a lot of quilting "Make it up as you go along" or have I just been lucky?
:D