I simply added borders to get to the desired size, basted and quilted as normal, then added a zippered back and machine-sewn binding.
A simple flap of folded fabric conceals the zipper:
A zippered cushion closure is so much nicer than an envelope backing - no gaping! - and is not at all difficult. I think I need to stock up on zippers and make a few more. My naked cushions would probably appreciate it. ;)
Bye for now,