This cushion cover is already sewn together with an overlapped fabric closure on the back, and with the sashiko design printed onto it in wash away print. You can just open the kit, thread the sashiko needle with the sashiko thread provided and start stitching your new project. Kit includes leather sashiko thimble as well as thread and needle. Finished size is about 17"x17".
You are meant to use the whole thickness of the sashiko thread included but some people do find it too thick to pull through the fabric comfortably. I find I can pull out a few strands to thin it down with no harm done. The stitches in these Olympus pre made kits are meant to be like short plump grains of rice and the thread does plump up with washing.
I really like these pre sewn Olympus sashiko kits. They've used a good mid-weight fabric and seams and zippers are well finished. I've made quite a few of them myself and there has always been enough thread with the kit. The projects can go in the washer and dryer so they are suitable for real life use, but they have the strong and elegant appeal of white on blue sashiko.