I have an obsession with white bed linen. I seriously think there is nothing better than sleeping between crisp white sheets... Recently I saw a gorgeous white duvet cover, but I just couldn't justify the expense, and then it hit me - I only ever use the fitted sheets, so there are a pile of flat white sheets in the linen cupboard.
I spread them out on my lounge floor and measured, cut, and pinned (a large job with a super king size bed!!), then sewed a stack of straight lines. I used the wide, top hem of the sheets for the button casement, and only had to cut two sides of each sheet to make the right size, so there wasn't too much work involved. Just stitching around the perimeter then sewing french seams down the cut sides to encase the raw edges, and voila, a brand new, crisp, white duvet cover for my bed.
And just in time for winter and 2 cats with muddy paws :-)