Voila! I started by marking the centre with some masking tape and just went from there with grey thread on top and white on the bottom.
The straight-ish lines are about 12mm apart. There were no major disasters. I have a couple of threads to pull to the back and knot where I either ran out of thread or had to unpick and re-sew.
I have some pink and a couple of the teals left to make a scrappy binding.