The zipper first. I like to put them about 2-3 inches up from the bottom seam line with a flange. It reduces bulk along the bottom of pillow. Easy to do.
Here is another method for zippers.
https://destashification.com/2011/12...n-free-zipper/
Another one too.
http://justgivemeaneedle.blogspot.co...ed-pillow.html