For this cake I baked three 9 inch rounds and leveled them off once they were cool. I iced them together the cut off bamboo skewers and stuck them thru the cake to make sure it didn't slide apart. I very lightly iced the outside of the cake with white icing and let it sit in the freezer overnight. In retrospect I would have made the layers different colors like in the rainbow cake and I would have made the initial light icing coat the same green as the final product. That initial coat of icing is supposed to be like primer is to painting a wall red, so next time I will go with tinted primer.
The next morning I got the cake out and iced the entire thing bright green. Now for the slightly (but not very) tricky part. I played around with different disposable cups until I found one that was the size I wanted the center and the petals. Then I cut off the bottom. I placed the cylinder in the center of the cake with the smaller side down and poured the white chocolate chips into the top of the cup. That way they go onto the cake in a perfect circle and it only takes a few minutes. (And I don't have to painfully place each chip.) Then I lines that center circle with cream colored icing.
For the petals I placed the larger part of the cup (the top) into the cake to mark off each circle. Then I lined them with yellow icing and filled them in with squiggles from a zip lock bag.
This is not the most complex cake in the world, but it was good fun.