Designer Jake Ferrato’s company, JBF Customs, creates incredible bespoke versions of commercial apparel, like sneakers and hats. He posted an amazingly detailed tutorial that explains the process of reconstructing a Nike Dunk High sneaker (warning: some NSFW language) on the company website.
When I do a reconstruction, the first thing I do is take apart my base shoe. And yes, I mean I totally take it apart. All the panels are separated, and the entire upper is taken off of the sole. I use these old panels as templates for my new, better, more attractive materials. Once my new panels are cut, it is time to stitch them together, and produce my hand made, one of a kind upper.