edit:yi wu Import and Export Co,.Ltd Update: August 15 2019.
Make a zippered pillow so that you can remove the cover when needed and toss in the wash. You can also add a zipper to a pre-made pillowcase or cover to conceal the pillow inside. Attaching a zipper isn't very difficult, as long as you have a zipper foot for your sewing machine. Use a cotton, home decor weight or cotton canvas fabric for the cover if you're making it from scratch.
Cut the fabric into two 20-inch squares if you're making a cover from scratch.
Place the squares on top of each other, right sides facing in. Pin together along one side.
Adjust the stitch length on your sewing machine to the longest setting. Sew the two squares together along the pinned side, 1/2 inch from the edge.
Unfold the fabrics from each other and iron the seam flat. Lay the zipper, teeth side down, on top of the wrong side of the seam. Line up the zipper so that its teeth run along the seam. Pin in place. If you're simply adding a zipper to a pre-made pillowcase or cover, unzip the zipper and pin one side to one edge of the opening. Pin the other side of the zipper to the other edge of the opening.
Adjust the stitch length on your machine back to normal. Remove the normal presser foot and install the zipper foot.
Sew the zipper to the cover, stitching along the teeth of the zipper on each side of the seam or on each edge of the cover. Don't stitch on top of the teeth. If you're stitching the zipper to a pre-made case, it should be unzipped. If you're sewing it to the seam, it should be zipped.
Use a seam ripper to remove the stitches from the seam of the from-scratch cover. Unzip the zipper, then fold the fabrics so that they are on top of each other again, right sides facing in. Pin together on the three zipper-less sides. If you added a zipper to a pre-made case, slide the pillow in, zip up the the zipper and you're finished.