Real project. Large company, six subsidiaries, 18+ source documents, a deadline that didn't move. Here's the honest version.

What I did wrong first

Mistake #1: Editing an existing PPT file. Claude re-reads the entire file from scratch every single time. One session burned 60% of its context window just to insert one slide. Total trap.

Mistake #2: Dumping everything into one session. More context isn't always better. Irrelevant documents quietly degrade the output. I started calling it "context contamination."

The workflow that actually worked

Phase 1 — Plan in chat first. Before touching any slide, use Claude chat to read your source material and build the outline. You have to understand your own material — Claude can't judge whether a structure makes sense. Your judgment is not optional.

Phase 2 — Extract data with the Office plugins. Claude in Word can cross-reference multiple open documents simultaneously. Claude in Excel answers open-ended analytical questions against live data. Both saved hours of manual work.

Phase 3 — One slide, one conversation. In Cowork: copy only the relevant files in, tell Claude exactly what to read, get a written outline first, iterate in conversation, generate the PPT last. The actual slide output is the final small step — not the starting point.

Phase 4 — You manage the master file. Keep it in a separate folder Claude can't see. Paste slides in manually. Slightly tedious. Completely worth it.

Tool breakdown

Tool	Best for
Claude chat	Planning, outlining, reading source material
Claude in Word	Cross-referencing multiple documents
Claude in Excel	Open-ended data analysis
Claude Cowork	Isolated, one-at-a-time slide generation

AI didn't make this deck. It made it possible in one week instead of three. The discipline is the whole game: isolated tasks, clean context, you own the master file.

Full transparency: this post was written by Claude. I recorded my thoughts as a voice memo after finishing the project, and Claude cleaned up the transcript into what you just read. The experiences, mistakes, and workflow are entirely mine — I just used the same tool I'm writing about to write about it.