The flat sheet size: 66" x 94". She needs a duvet cover size: 36"x50". I fold the flat sheet in half, and measure the length and width I needed and make marks. ( remember to leave seam allowances)
Since the flat sheet is folded in half, one of the side didn't need to sewn together.
Duvet cover is done.
If you'r making an adult size duvet cover, take 2 flat sheets ( every sheet set will include one flat sheet, which means you will need 2 sheet sets. The duvet cover will be reversible)
There are many options for the closure of the duvet cover, you can make botton holes, or sewn ribbons and tie them as closure, or hand sewn some snap buttons on.
Thank you for reading : )