The blossom of a Dahlia is set directly on a boxlite 40; the camera is shooting vertically down. (Switch off the modeling light of the boxlite, otherwise the flower is withered before you shot it.)
In a first step, the power of the boxlite is adjusted: It is as bright as possible, but only very small parts of the flower should be burnt.
Then, the picolite with its fresnel spot attachment is positioned very close to the object. The light is not aiming directly to the flower, but a little higher. Like this, the light only hits the center of the blossom, leaving other leaves more in the dark - these leaves only get the light from the boxlite below.
A second advantage of this position of the picolite is, that there is enough light to be reflected back to the blossom with a concave mirror. This creates additional highlights where the picolite does not reach.
