Wall structure of dormer roof

Hello everyone,

I have a question about the correct execution of the wall structure of a dormer.

We have a carpenter-style flat roof dormer on our garage roof. It is erected in timber frame construction (200mm beams) and clad on the outside with OSB boards (22mm). Over the entire OSB sheathing (except for the window openings), an underlayment membrane (Rewasi Top) has been installed. The roof is already covered with titanium zinc sheet.

Now my question about the professionally correct construction on the outside. We would like to clad the side walls and the front wall with horizontally attached wooden battens or similar. How should these be properly fastened? Simply screw a vertical lathing onto the OSB boards and then screw the cladding onto that?

I am a bit concerned that water might get behind the cladding and cause problems there. Or can the USB handle all of this? Perhaps it is also important to know that there is hardly any roof overhang, but drip edges are present at the upper edge on the sides and front.
I hope I have expressed myself clearly enough.