My small Stevenson screen box  the door Wooden slatsis are slowly rotting away, so I've replaced it with a home-made double lever door Which is very easy to make. I made a small frame using some hardwood on the inside of the frame a series of holes were drilled. These holes are where the dowels lock into place

New double louvre door
Top, bottom, sides are made up with three sheets of 5 mm plastic to the thickness of 15 millimetres the middle sheet is black
To make the wooden double louvre doors slats , you need a length of 90 angle wooden architrave and a length of dowel rod
Cut the wood so it fit inside your door  frame and cut the dowel with a excess of 5 mm each end.  Glue the dowel so it runs inside of the 90 angle wooden pieces
I Could only get softwood for the slats. To protect them from the elements.  I  painted three coats of wood Preservative primer, followed by a coat of undercoat paint then two coats of Outdoor Satin finish paint.

Using this technique you could very easily make a Stevenson screen box using double louvre all round
It's important when you drill the holes inside the frame that they match your dowel inserts you want them as tight as you can, but also allowing them to be adjusted.. If you do not want your louvred door slats to be adjustable then, but some glue on the end of the dowel before pushing them into the holes
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small Stevenson screen box