Henry explained how to attach the flats in the simplest way to make the strongest room. Always start in the corner with two people firmly holding the flats together making sure with a spirit level that they are straight and also that they are at a right angle. After a corner is created the room can be built from there, attaching the flats to one another by screwing the two long sides together always starting at the bottom and always making sure the flats are flush together as you move up the flat.