This chapter from Sandra Betzina Sews For Your Home features a lesson on learning to sew a duvet cover.
Making items for your home can be more satisfying than any sewing you have ever done. It's your chance to infuse your personality and creative ideas into the objects you see and use everyday, and you'll save a bundle of money in the process. Whether you are outfitting your first apartment or downsizing after the children have left home, it's easy to make your surroundings reflect your personality, needs, and tastes.
This publication is from the section on sleeping comfort, are complete instructions for making a duvet cover.
You can also learn how to sew a duvet cover at http://powersewing.tv/episode/036-sewing-duvet-cover