This works perfect for 12X20 pillows, it may similarly for other rectangle pillows, as long as they are close to the same size.
The Easiest No Sew DIY Pillowcase
Over the years I've found myself with a collection of cloth seasonal and holiday placemats that I no longer use. This is the simplest way to recycle those placemats into useful decorative pillowcases. And the best part is that they are no sew!
The placemat needs to be a lined place mat, two pieces of material sewn together. You will begin by simply cutting the back layer of the material. Cut in the middle, all the way from bottom to top.
Once you are done cutting, this should have created a pocket in the back of the placemat.
Next stuff the pillow into the pocket. This may take a bit to get the pillow in there completely.
The back will not close once the pillow is in there, which is ok! If it bothers you, you can always add materials or fabric tape to help keep it closed. Once it's flipped over, you will not see it though. Smooth out your pillow and the placemat until it lays nicely.
Flip it over and there's your 3 step seasonal pillowcase! No mess, no sewing.