duncan's schema of class planning
What is the skill you want them to have? Specify it. Ideally you want a skill0using activity, and stepping through that activity helps you write the specification of the skill.
Step through that skill execution. Every time you encounter a component that needs more explanation, note it down. That is your list of component modules.
Repeat 1 and 2 for each item in that list until you have a concept DAG.
Order and chunk stuff together. Write cute explanations for things.