Best to use when
The final storyboard is the final Converge exercise and should be used to focus on what the team will be prototyping. This should be done on a whiteboard so everyone can see it. Start by drawing a comic book frame for each single action in the critical path. Don't worry too much about layout or design details, as this will be refined in the Prototyping Phase.
Revisit how to Story Board.
After reviewing Assumptions, Backburner Board, Identifying Conflicting ideas on how to solve a problem, the group should come together to decide on one direction for the prototype.
The facilitator should stand at the whiteboard and draw out a frame-by-frame as the group decides the final user flow of the app and the pieces that should be prototyped.