To create a negative image, place the leaf onto the inked gelatin plate. Site has stellar photo tutorial, particularly creating the large gel plate. Artist uses coffee filters but pretty sure light muslin will work also .
Andy Skinner stencils and a Gelli Plate. fast forward video demonstrating how to create a picture using your Gelli plate and stencils and how to put the finishing touches on it. Love this artist's gelli prints and stencils.