Funnel Process PowerPoint Diagram. The funnel diagram is going to help you when you want to present processes where users must complete stages and advance into the funnel. One common use of this type of diagram is to design marketing funnels or buying funnels, where the user must advance steps that will lead him or her to complete a purchase. The template can be used as is or you can change it and adapt it to your needs. It is made completely in PowerPoint and the shapes remain editable.