We had a Moselle with the L-shaped lounge and the best way we found of making up the bed was to store the two back corner pieces in the compartment under the seat and use the other lengths of the back supports laid flat running down the left hand side. Leave the seat part by the window in place and after you pull out the slats lay the other seat onto that. If you dont want any lumps from the knee supports turn both seats upside down for a flatter surface.
Any cushions can be stores under the bed when made up.