From yet another Craftsy pattern, for yet another relative's Christmas present, it's about 12 inches.
It's not perfect- you can see the two halves are slightly misaligned- but I'm pretty happy with it.
I'd call it a high beginner pattern. It was pretty easy, with big pieces for the most part, and even the small pieces were easy. I wouldn't advise it as a first pattern, but maybe as a second paper piecing project it would be fine.
The pattern has so much potential for variation- you could use two fabrics for the interlocking strips, or just one with a strongly contrasting backing. It would be gorgeous in batiks, cat fabrics, solids, whatever. You could have so much fun trying different combinations and I pieced the top in two afternoons, about 3 hours of work, with another hour to quilt it by machine and finish it into a pillow.
I used scraps for both the strips and the background.
If you're not using scraps, you'd need a fat quarter of each fabric if you're using 2 for the strips, or a half yard if you're using 1 for the strips and a fat quarter for the background (about). I always err on the side of having more fabric than necessary and I don't want to make promises but I think that would do it.