I made the graph in Stylecraft Special DK using –
White 1001 – 100 grams
Black 1002 – 200 grams
4.00 mm hook
With a double crochet stitch (UK terminology)
The cushion size was a 20 inch square. I joined the two parts of the cushion with a round of double crochet in black and then another round in white. There is no graph for the back as it was done in black.