There are some useful resources online the DipTESOL phonology interview. You can find two great overviews about it from Gemma Lunn and Dave Dodgson. Both mention the example videos by Oxford TEFL, which I think are done by the tutors there.
All I can really add are some concrete examples, and a bit about my experience of doing the interview itself.
Just for context, I got a Distinction for the DipTESOL. I scored 82 for my assignments – you can read a summary of one here and find the others in English Teaching Professional (see ‘About me’). I got 83 (I think) for the phonology interview, 81 for the teaching practice and 73 for the exam. However, I’m not a Dip examiner or tutor, so I can only share my subjective views…
I presented about activities I use to raise awareness of contrastive stress. I mentioned:
- a specific group of learners
- WHY this was an important or relevant skill for them to practice
- how I got students to notice contrastive stress
- how I got them to practice it
- how I encouraged them to produce this feature in a freer context