I decided that I couldn't just let it lie around being another UFO. I got out the left-over bamboo batting, put a backing on using a piece of fabric that I had bought to trial as the optical illusion solid colour but rejected for the darker fuchsia colour, and sewed it all together.
I looked at the designs in the books I got from Dijanne Cevaal and found one I liked. A wavy grid that I hoped would subtly disguise the non-matching corners.
But the sewing has disguised the uneven squares quite adequately.