I picked up two yards of fabric. I cut out the top and bottom of the cushion, with an extra two inches on every side. Then I cut out the four sides. I sewed three sides to the top (the two long sides and one of the shorter sides). Then I sewed the same three sides to the bottom.
Next, I shoved, yes shoved, the cushion into the cover and pinned the fourth side. I used the machine to sew one of the longer seams, and again shoved the cushion inside the cover.
I hand sewed the rest of the three seams. I think it turned out pretty good. And Foxy still loves to cuddle up on the cushion.
All in all I consider this a great success!