When I made my first bellows I used some cloth from the fabric store that was as light blocking as I could find while being fairly thin. I bought some thin blank liner also. Then I made a layout on very thin Kraft paper and glued stiffeners onto it. Over that I glued, with spray adhesive again, a layer of tin foil. Over the tin foil I glued the backing cloth. Then I folded and glued the overlap together. I don't have the bellows out to photograph it right now but some thirty years later it doesn't leak. It's been sitting most of the time. I made the camera out if Brass and Cherry predominately with hand tools. The key is light tight and flexible.
For my new project I had an 11x14 bellows made. I do believe in self made though as much as possible. When I get up my horses I'm completing the 11x14 film holders I started. I made a traditional holder and it's nearly identical to the original specifications laid out a century ago. now with the working holder and the drawings I can go at will.