Leaders build trust by backing their team through mistakes. When you assign someone a stretch task, make clear it's a vote of confidence. If they fail, coach them instead of punishing them. That's how people learn to take risks.
Chapters
Lastly, I would say they need to know that you have their back. They need to know that if they are given an assignment that they're not really familiar with, they're not really skilled at, one, you've given it to them because you trust them and that, and you want to help and stretch them. At the same time, should they screw up, should they make a mistake, should they fail at accomplishing what it is that they were supposed to be doing? They want to know that they're not going to get reprimanded or not going to get disciplined, but they're going to be supported. They're going to be coached. They're going to be developed. They're going to have someone that they can trust that will have their back, whether things go right or when things go wrong.