Very easy ! Pick up a non-elastic yarn like the blend cotton-acryl from DROPS I have used, and a crochet a little under the number advised for the yarn (I have used a 4 mm instead of 5 or 6) so that the result is stiff. And off you are, with a spiralling project (no join in the round, you just crochet a continuous spiral). It is single crochet all along - just one "round" done in the back loops. Go for it ! It is fun to do, and highly customizable.