I know this is a little too late but here is what I do with pillows...
I use pillow forms rather then loose fiber fill. So say I have an 18" pillow form. I make my block so it is around 20" square. Then I cut two pieces of fabric for the back of the pillow 20" by 12 1/2". I turn under a hem on one of the 20" sides on each piece of the backing fabric and sew it. With right sides together I sew on one and then the other so it is overlapping the first, the hemmed sides at the opening. This creates like a pillow sham with a finished overlapping opening in the back. I turn the thing right side out and I slide my pillow form in and that way if (or should I say when) the pillow gets dirty I can remove the pillow form and toss the sham in the washer. I have never tried this method with piping but I have done it with a ruffle and it works well. The overlap of approximately 3 1/2 to 4" inches doesn't open up in the back either. Hope this explanation makes sense.