Here's how to create an environment where your team feel safe to volunteer error.
1. Overemphasize your own sub-standard execution. (This is the fastest and most powerful way.)
2. Ensure the team understands that the purpose of the debrief is to increase team performance. Not to allocate blame, nor punish anyone for 'honest mistakes'.
3. Use a third-person narrative and refer to people by position title, not name.
4. Compare behavior to ideal organisational behaviour (which should be written down and well-known).
5. Always use non-emotive language, remain clinical and display as much empathy as possible.