It's not always easy to find single sheets of the appropriate size, but you can often get lucky in discount stores and clearance sections. When you find two coordinating ones and pillow cases that will match, you're ready to go.
Sew the sheets together along the edges, leaving about 2/3 of one edge open. That edge should be the one with the larger hem. Sew to the inner side of that hem so that it doesn't show when you turn the cover inside out. It will also give extra reinforcement layers of fabric for buttons and button holes if you wish to use those for closing the cover.
You may also sew strips of grosgrain ribbon about 8 inches apart to each side of the opening and tie them to close the opening. Use the pillowcases as pillow shams. Enjoy your creativity!
By Pat C from NY
If you are able to make button holes I suggest making them at either end and adding appropriate size buttons. This way you can button cover to comforter and not fight with it falling down into the bottom or away from the sides. That's what I hate about the covers.
I used sheets to make my covers. Just sewed togther three sides. I sewed the sides and bottom of sheets. Then on the other end, I made button holes on one, the buttons on the other. Then I could just slide in the comforter and button it. Sheets are easy to wash, dry fast, and are cheap. Need to use two flat sheets to do this.
By Linholly from Central, ME