First, I separated the stem and leaves from the flower head. Then poured gesso into the bowl (just enough to cover the flower). Now, I had white gesso, but as I mentioned it can be bought pre-colored or is easy enough to tint it yourself. The trick when you dip the flower into the gesso is to make the coverage very light, otherwise, the petals will get heavy and hardly manageable...gently squeeze the flower as to remove all the excess gesso. After that, let the flowers completely dry out (around 8 hours). Shiny parts on the surface of the flower are a signal that the gesso is not yet fully dry.
Occasionally during the drying process, I was separating any petals that had stuck together, so they wouldn't stay stuck together and make the flower look flat. If you want, you can add more body to your flower by applying more gesso with a brush as a second layer.