The instruction that seems complete to its author may still need a beginner’s eyes.

Whoever wrote the instructions cannot un-know the thing the instructions assume. The step that is missing is missing precisely because it is automatic to them, so rereading their own work confirms nothing; they fill the gap silently every time. Only someone who does not already know can show you where the path disappears.

Hand your instructions to a person who has never done the task, and then sit quietly while they try. The rule is to say nothing until they finish or get properly stuck. Write down every place they hesitate, because hesitation marks the gap more reliably than their opinion of the document afterward.