I was inspired by this pillow from dedeetsyshop:
Image from dedeetsyshop.etsy.com
I used blue linen for the pillow cover and white linen for the rosette. The pillow cover is a simple envelope cover. The rosette was made by cutting one long strip of white linen, about three inches wide. Setting my sewing machine to the widest stitch and the highest tension, I sewed a gathering stitch along one of the long edges. When through, I pulled on the ends of the thread to gather the fabric.
I pinned it into place on the pillow cover to form a rosette, then sewed it on at the gathered edge. I finished off the middle of the rosette with a circle of linen and a white vintage button.