Use 4 or 5 different colour cones across the field.
Call a player and a cone colour.
Player simulates as if he's made the tackle. The rest of the team sets up quickly as if they were defending that part of the field.
Call the next player & colour and get them to reload into defence there.
Progressions:
An attack after a few reps of defence is a good reward for a team who is energetic and getting their structure correct.
A mistake on attack (e.g. a ball knocked on) gets the team back into defensive mode.
Create a resolution to develop your coaching confidence by seizing the opportunity to discover new drills, turn ideas into action and seek advice from the coaching community.
World Rugby has reportedly conceded Aaron Smith's disallowed try in the World Cup final should have stood.
"It is not only useful for staff who are experienced but a valuable tool for those subject staff who have to take teams."