Write down all the reasons why your company would want to spend money on this project in the first place.
Then pick and highlight the most important one.
If you could walk into a store, and buy the shrink wrapped version of your software, what the design of the box look like and what would it say?
Point here is to get your team looking at your project through the eyes of your end customer.
Give your sponsors some idea of how big this thing is (1, 3, or 6 monther).
Before you can complete this slide you and the team should create and estimate a high-level story list for the project.
This isn’t a commitment (too many unknowns). It’s just a really rough guess. Don’t treat it as anything else.