Audience-specific talk decks with a custom GPT and Gamma
Sophie Hundertmark
Sophie Hundertmark, an AI consultant and lecturer, built a custom GPT from six of her past talks so it writes slide text in her voice, then pastes the text into Gamma Pro to design each deck. She says a ready-to-use deck takes under an hour, plus 10 to 15 minutes of checking after the PowerPoint export (self-reported).
Story written by: the person who did it
The problem
Sophie Hundertmark gives several talks a week, and each event has a different audience, from students to managers to specialist groups. Reusing old decks with small changes felt impersonal and did not always fit the target group. Building every deck by hand in PowerPoint took many hours of writing, design work and image searching.
How it was built
- 1Build style guidelines from old talksCustom GPT
- 2Create the custom GPTCustom GPT
- 3Give the brief for each new talkCustom GPT
- 4Generate the slide textCustom GPT
- 5Paste the text into GammaGamma Pro
- 6Export to PowerPoint and check every slidePowerPoint
Tool step Person step
1. Build style guidelines from old talks
She gave ChatGPT six of her past presentations and had it write guidelines for her content structure and tone of voice.
ToolCustom GPT
2. Create the custom GPT
She pasted those guidelines into her own custom GPT as its system prompt; the GPT is based on OpenAI's GPT-5 language model. Her exact prompt is not published.
ToolCustom GPT
Check: She makes sure the guidelines cover tone, style and her typical structure, so the GPT writes the way she needs it to.
3. Give the brief for each new talk
The custom GPT asks for the target group, the length of the talk, a title wish, an abstract or background information, her own content ideas and any documents to upload.
ToolCustom GPT
Check: She sets the direction and adds her own ideas before the GPT writes anything.
4. Generate the slide text
The custom GPT writes complete slide text in a few minutes, in her style. For one talk on AI and customer experience, she gave it an abstract, a few key theses and an uploaded white paper to back up the content.
ToolCustom GPT
Check: She brings her own expertise to the input so the text carries her ideas, not just machine output.
5. Paste the text into Gamma
She copies the GPT's text into Gamma Pro, which builds a full slide deck from it in seconds, and she picks colours, fonts and image style so the deck matches her branding.
ToolGamma Pro
6. Export to PowerPoint and check every slide
She exports the deck to PowerPoint so she can adjust it by hand. The export does not always work perfectly: layouts or single design elements can slip out of place.
ToolPowerPoint
Check: She checks the slides thoroughly before each use and allows 10 to 15 minutes of post-production per deck.
Before and after
Before
She reused old decks with small changes, which felt impersonal and did not always fit the audience, or she spent many hours in PowerPoint writing content, adjusting designs and searching for images.
After
She says she has a complete, ready-to-use deck in less than an hour, each one tailored to its audience and kept in her personal style (self-reported). source
What made it work
- The custom GPT learned from her own past talks, so every new deck keeps her personal style.
- She gives the GPT a clear brief each time: audience, length, title, abstract, her own ideas and supporting documents.
- She adds her own ideas and expertise; the AI does the heavy writing, not the thinking.
- Gamma Pro turns the text into a designed deck in seconds, with her colours, fonts and image style.
- She always checks the exported slides and fixes anything that slipped before using them.
Follow along
Practice steps suggested by Ai Siftly, based on the account above. We have not run them ourselves.
Example to copy: Describe structure, tone, titles and detail level in these decks. Separate observations from guesses. [excerpts]
You should get: Edited style guide.
Check: Remove patterns that do not sound like you.
Example to copy: Audience:[who]. Goal:[action]. Length:[minutes/slides]. Key points:[list]. Approved facts:[sources]. Style:[guide]. Ask about missing essentials.
You should get: Clarified brief.
Check: Audience, goal and main claim resolved.
Example to copy: For each slide: point-title, supporting text, source, visual suggestion. Mark unsupported claims CHECK. No invented data.
You should get: Editable slide outline.
Check: Resolve CHECK items; ending supports goal.
You should get: A working deck that still needs review, with review time allowed.
Check: Check reading order, density, rights and factual integrity; no seconds-to-finish guarantee.
You should get: Inspected deck.
Check: Fix shifted text, fonts, images and charts; rehearse timing.
Try it yourself
Find a matching workflow in the workflow finder. Search words: c u s t o m G P T p r e s e n t a t i o n s l i d e s G a m m a.
Sources and notes
- Create presentations with: My workflow with CustomGPT and Gamma (sophiehundertmark.com, 2025-09-02)
- All time figures are self-reported by Sophie Hundertmark on her own site; she gives no measurement method.
- She sells AI consulting, so read her results as her own account of her workflow.
- Her exact custom GPT prompt from September 2025 is not published.
- She says the PowerPoint export can shift layouts, and deeply scientific topics still need a lot of your own work.
- Have ready: two short excerpts from your own nonconfidential decks (or your written style preferences), your talk brief with approved facts, and a presentation editor you may use.
- The follow-along steps are Ai Siftly's suggested practice, not her exact process.
No measurement method Author sells AI consulting Custom GPT prompt not published. Date note: 2025-09-02. Record dated 2026-10-27.