Using the centre roof tab to the front and rear and the ring to the centre of the unit as a guide, fold the unit in half along its length.
Fold the front (bow end) of the unit at the first break (A) in the bottom of the skirt making sure that the edge of the unit stays in line.
Fold the front (bow end) window back
Fold the back (stern) panel over at break B in the bottom of the skirt.
Fold in half to form a long rectangle that is slightly narrower than the bag.
Fold the grey over the side panel.
Starting at the bottom, roll up the unit being careful to exclude as much air as possible.
Doing this twice in quick succession works well.