I’ve seen this first hand on Ariana Afghan Airlines, but without seatbelts or stools. Instead, just grab onto the piles of luggage in the back of the plane and hang on!
This is the chair I sat in while going from Papeete to Moorea in the mid 90s. There were 4 on the plane and mine was next to the pilot! Thank God is was less than a 20 mile ride.....