I'd been thinking about using a cross stitch pattern for a while (they are basically the same after all) but it's tough finding a small simple one. This is Martha Stewart one is free on her website!
Where there is a half stitch in the pattern I do a whole stitch - I didn't on the birds right leg and you can see it looks a bit weird.
Cast on to match width of cushion (mine was 70 stitches)
4 rows double rib
Cast of one stitch on next row
Knit row, purl row until you can cover one side of your cushion
Knit 14 - pattern - knit 14
Purl 14 - pattern - purl 14
knit row, purl row until your work covers the cushion
6 rows double rib - If you would like button wholes cast off 2 stitches where you would like them on the 3rd row and add 2 back in above them on the 4th row.
Pin inside out against cushion (remove cushion if it's in there) sew up long edges - I normally chain crochet as it's quick and neat.