Doodling in the round is satisfying because it has no beginning or ending.
Start by creating your flower heads. Within the circle provided draw five or any (odd) number of smaller round shapes. Scatter them throughout the circle. These will be your flower blossoms so decide what type you want.
Daisies have a small center and radial petals coming out from it, roses have wavy lines that get smaller and closer as they go toward the center. Hydrangeas are cluster blossoms, comprised of many much smaller individual flowers. Next are the curvy, double lines for stems done in pencil going around the page and linking the blossoms. Leaves can be placed anywhere, coming off the stems. Finally add buds.
Study your composition until it is as you want it. All is left is to shade it with your pencil or tint it with colored pencils. A solid background can be added or leave it white.
Time to do another one, practice, experiment, be safe or take risks, but above all, remember there are no judges.
This is your journal, so have fun.