Pick a method or process that you have used many times through your PhD. It might involve special equipment or software, precious resources or simply be related to how you get something from journal articles.
Now write the procedure out step by step. Start at the beginning and work through how you would use it to whatever the goal is. Unpick the stages and what triggers them, whether it’s simply moving on to the next piece of work or reaching a certain condition.
“How do you do it?” is a less common question at the viva maybe, but it’s in the background of many candidate concerns about being good enough, knowing enough and feeling confident. If you’re sure that you know how to do something then you have one less thing to worry about.
Find something you have used a lot and take it apart. Be certain of all the steps. Then use this as one more example of something you’re good at; it can help you to show others what you know, but also demonstrate to yourself that you are good.