Unfortunately scratch building has become something of a lost art. These are some book I have found to be useful. https://www.amazon.com/Master-Scratch-Builders-Aircraft-Techniques/dp/0764307959
https://www.amazon.com/Model-Building-Brass-Kenneth-Foran/dp/0764340042/ref=sr_1_4?dchild=1&keywords=Modeling+in+brass&qid=1612025108&s=books&sr=1-4
https://www.amazon.com/More-Scratchbuilding-Masterclass-Chris-Meddings/dp/0993258840/ref=sr_1_10?dchild=1&keywords=scratchbuilding&qid=1612025058&s=books&sr=1-10
Arizona models sell both a kit and plans in 1/6th scale for the Fokker DVII
https://arizonamodels.com/products/fokker-dvii
They also sell engine kits. spandau guns and lozenge pattern Covering.
Scratch building involves a lot of different skills. For ww1 aircraft you usually start with the cross sections, or bulkheads, and then attached them together with formers https://thevintageaviator.co.nz/projects/fokker-dvii-build That gives you the basic shape and that gets covered with fabric and doped. The fokker had a Aluminum Frame so if you do that you will have a bit of soldering to do. The modeling in brass book may help. Whatever you do start with good plans. I would start with smaller parts and workout any kinks in building methods. Start with the Rudder and Elevators first.