I have never undertaken a project for anyone without having detailed shop drawings to work from.
I have done a lot of work "on the fly", without drawings. But those were always pieces or projects I was either doing for myself or on spec. James Krenov called working like this composing. Most of the rest of us call it making it up as you go. There is nothing wrong with making it up as you go. But not when you are working for someone else.
So if we take it as a given that custom work should always be done from drawings, the next question to arise is who is doing the drawings. I have gotten drawings from architects, designers, contractors and sometimes, from the customers themselves. But I never did a job without making my own shop drawings. My drawings were invariably more specific both in detail and dimension that those provided by others.
I came to realize that there could be significant discrepancies between my drawings and those provided by others. Mostly this was because my drawings were based on actual on-site measurements and layouts that took into account the fact that a 3/4" thick end panel is actually 3/4" thick, unlike the pencil line on the architect's plan.
Ultimately, I included a clause in my contracts that stated that my shop drawings were the governing document. I required that these drawings be signed off by any and all interested parties. This included the architect, the designer, the future installer and the customer. I would spend as much time as necessary altering the drawings to reflect the intent of the design and in measuring and laying out, on the job site, all pieces of casework that would ultimately be installed.
Once these drawings were approved, I would never deviate from them without going back and having all those who signed off on them approve the change. When the job was delivered, I could point to any piece of woodwork and correlate it to the approved drawings.