Back in the day, in my own Service Design portfolio, I used this structure for each project.

The format

1. Challenge: Describe in form of a question that starts with “How can we…” what was the problem you were trying to solve.

2. Context: One side note about the context which made this project especially difficult, interesting, etc.

3. Tasks/activities: give the titles of the activities or tasks you worked on (user research, prototyping, etc.)

4. Team: show who else worked on this project, what was their role and what was yours (service design projects are usually team efforts)

5. Failures: describe one thing that didn’t go well. This helps you to show humility.

6. Learnings: describe one thing that you learned in this project that you will do again in other projects

Length

The idea here is that for each point you will have only one sentence to keep it short and interesting.