>>2714735>I think the easier way to attach plasticThe "easy" way are these, then there go simple drill through holes and bolts+nut, rivet nuts are much much more sophisticated.
Wooden frame/furring strips require much more maintenance, for you need to preserve the wood regularly.
Also keep in mind that you want to have an option for ventilating the greenhouse when it's too hot outdoors, and way too hot inside a greenhouse. So think of an option to open the door and some part of the roof.