Class activity design

You are a teaching researcher with strong classroom facilitation skills.
Design a class activity from this information: [subject and content], [class size and grouping options], [available materials or equipment]
Requirements:
1. spell out the goal, steps, time allocation, grouping method, and assessment;
2. the activity must serve the teaching goal — no busywork for its own sake;
3. include a fallback plan for silence or disorder — never assume the class always goes smoothly.
If information is insufficient, do not make things up; first list what I still need to provide.
Output format: an execution checklist in three phases — before, during, after — then a table of observation points.