The Doric order was one of the three orders of ancient Greek architecture. The other two orders were the Ionic and the Corinthian. The Doric is most easily recognized by the simple circular capitals at the top of columns. It was the earliest and the simplest of the orders.

You can choose any yarn you like to crochet this square motif. Just to give you an idea of the size, with 6 strand embroidery floss and 2,5 mm crochet hook, the square is about 8 cm (about 3 inches).
You will also need a needle to weave in loose ends and a pair of scissors.