Measure your duvet insert
Choose fabric and wash it first
Cut two fabric panels to size
Add seam allowance to all sides
Finish the edges of the opening
Place the panels right sides together
Pin or clip the edges
Sew around three sides and part of the fourth
Reinforce the corners if needed
Turn the cover right side out
Press the seams flat
Add closures such as buttons, snaps, ties, or a zipper
Insert the duvet
Close the opening