What I used
-Seven yards of the softest linen I could find ($15/yard for my king-sized bed)
What I did: I had this amazing long fringe trim leftover from a previous project, so I dyed it along with the fabric. I used a king-size sheet as a pattern and cut the fabric into the same shape and dimension as the sheet. (I had to sew two pieces of fabric together to make one large square.)
Next I sewed the trim onto two opposite sides of the square. I then took the sheet and sewed it to three of the four sides of the large linen square. (I sewed it inside-out so that the seams would be hidden on the inside.) I left the top side open so that there would be a place for the blanket. I then sewed on a few buttons and cut some button holes to match on the open side.
*Be sure to run your washer alone after using it to dye anything or risk turning your next wash-cycle teal!
**Wash alone the first few times you wash the duvet.