Each layer of this double layered flower is made with the instructions below. You can make flowers with as many layers as you want. The trick is to use different sizes of yarns and hooks.

You can choose any yarn you like to crochet this flower. Just to give you an idea of the size, with cotton thread size 10 and a 2 mm crochet hook, the flower is going to be about 5 cm (about 2 inches) in diameter.
You will also need a needle to weave in loose ends and a pair of scissors.