It didn't take too long to make these and to get the size I just measured the yucky old covers and made a pattern piece. I love the fabric and it's nice to finally replace the gross, old covers. I cut the fabric out with pinking shears rather than overlocking the seams, but I don't know if that's really a good way to stop this drill-type of fabric fraying - time will tell.
Now on to the zippers. The cushion on the right is the first one I made up and you can see the zipper tabs are poking out. I mostly fixed this on the left cushion by moving the zipper off centre so one of the ends would be caught in the 1.5cm side seam, and pushed the second tab down into the seam allowance. This looks better - but not 100%. Someone has suggested trying an in-seam zip next time or if I go the exposed zip route then put some fabric over the zipper ends - like this tutorial.
So whilst these aren't perfect the are fun and functional. The zippers are at the bottom of the cushions so the flaws are well hidden.