Arrange four chairs in a small square, facing inwards. Choose four volunteers (of roughly equal height and weight) and ask them to sit sideways on the chairs with their legs to the left of the seat. Ask four more volunteers to stand behind the chairs.
The people sitting on the chairs should lean backwards until their head, shoulders, and upper back are resting on the knees behind them. When everyone is comfortable ask them to lift up their hips slightly and the people standing behind them should carefully slide the chairs out from under them. The four people should remain supported without the chairs. After a minute replace the chairs so no-one falls on the floor! You may need to allow time to repeat this activity so that others can have a turn.