The outer covering (below left) is laced by 4 central tucked bands (below right) which is held in place with a centrally tied 'rope'.
The cords were cut away/unlaced around the upper section & the underneath panel (below) then the outer 'corset' was removed.
The individual pieces can now be cleaned & repaired as the entire outer 'bag' (below) has a zip to insert the inner seat (as per Pouffe here).