I can only explain it in 45 minutes…
I often get this issue in client discussions. So we start out, and in that first meeting, it often turns out that the client can explain it in 5 to 10 minutes. The difference? Me impolitely interrupting monologues where I got the point already, and asking questions inviting conversation about issues that are not covered.
How to do it without the help of a probing presentation designer? Take a radical approach to how much time you spend on each element of your story. If a certain section is incredibly important, but at the same time totally obvious, old news, and well known, cut it to the minimum. On the other hand there might be a tiny detail that is completely counter intuitive and merits a total 5 minute deep dive.
You are not writing an essay about your brilliant idea, you are racing against the clock to explain your idea in 5–10 minutes.
I admit that this is easier to do in 1–1 conversations than in formal presentations. Test your story in 1–1 conversations with smart people before pitching it to larger audiences.