This guide assumes you know how to make the basic crochet stitches. This is not the guide to teach you the complete entry-level basics, sorry!
Glossary: UK/US terms; slst/slst, tr/dc, ch/ch. We use treble in place of the US double.
If this is big enough, great! You now need to just complete enough rows as necessary to give you the length you need as follows; ch3, tr in first tr, tr in each st around, join with a slst.
If this is not big enough to fit yet, you need to do some more rows, according to the pattern. Follow row 2, 3 and 4 until it is big enough. Then you can tr in each stitch to provide length.
I will be writing a flower tutorial (and a pompon one, if anyone would like one, let me know by message)... Any questions, please let me know :)