1 Choose your grade band
Sets the grade context for the unit.
And your curriculum framework. Concept-based design isn't IB-specific: the framework tags your unit and shapes the assessment layer where a framework-specific layer exists.
2 Choose the driving structure
Every subject contains both, you pick the one that drives this unit.
3 Choose your subject
4 Before you start: the interplay
No subject is purely one structure. Maths and Science have processes; Language and the Arts rest on knowledge. You've named the structure that drives this unit, the planner keeps the other in view.
Why? Understanding is generated in the movement between the two levels of thinking, the factual/skill level and the conceptual level, the interplay concept-based authors call synergistic thinking: not climbing from facts to concepts once, but moving between them until students can think with the idea in a new context. Every prompt in this planner is built to provoke that movement.