You are pretty much dead in the water if you start without a pattern. My restoration started with sketching / tracing / photos etc. of existing wood work before any dismantling was done, even rotted wood can be held together temporarily with glue or tape so as to try and get some sort of pattern.
Having done that you pretty much remove (carefully) the metal skin from the existing wood work and do your cleaning / rust repairs / panel beating etc.
Sort out your timber requirements (quality hard woods are a must, proper graining etc.)- seek advice if you are unsure, remember this is the internal strength to you body work.
Now its a matter of shaping / cutting / sanding the skeleton from this timber to form your shapes to support the metal panels. I worked with one panel at a time ie rear tub, front cowl then to doors and so on, of course you will also have to cut and shape the under frame which goes between the body and the chassis; this will support the steel brackets which hold your upper body framework to the chassis. Generally you will then have to fix your metal panels to this skeleton with nails / screws, glues etc.
The real fun part begins when you get to fitting the doors,hoods and access panels; be prepared for lots of cursing and swearing as you try to get the door gaps right, hinges hung correctly and so on. Dont be too proud to use scraps of timber for hidden packers / spacers etc.to achieve some form of alignment because if you had the luxury of dismantling the body in the first place you will find thats how they were when they left the factory !!
All sound too hard? just persevere its worth the effort and dont plan on getting it right first time around.
Good luck
CJH