You can use anything, I'm using felt tips.
Start with a circle and decorate inside.
Add petals and decorate inside them too :)
And some more and make them smaller
Then add bigger petals and decorate them too
Keep adding more and more ...
Nearly done :)
Add two lines between the petals
Shade in half of the petals with a black colouring in pencil
Now you can colour in the petals
The creator of this guide has not included tools