When I was little, we had a View-Master viewer Model C (which I still have) and a bunch of reels. At that time you could go down to the department store and buy reels on all kinds of subjects: mostly travel, but movies and tv shows used to put out stills on reels. (Later on View-Master went down-market and became a kid's toy.) It wasn't until I was a lot older that I realized the 3D effect and how interesting it was. And it never occurred to me you could own a camera that took the stereo pairs and you could buy blanks and make reels yourself. And it's probably for the best, because I would have gone nuts about it if I'd known.
A blown opportunity or two, and I finally got one from eBay. View-Master images are tiny, and they do it by taking half-frame photos width-wise—meaning you can two rows of images across a length of film. The camera does this by using an ingenious reversing mechanism and four shutters (two shutters on each lens). You set the direction to shoot, and you take your pairs. When you run the length of the film, you turn the knob to reverse the film direction and switch to the other shutters, and you take the rest of your photos. You can get a helluva lot of exposures on a single roll of 35mm.
This also required a film cutter, though you could get by without one if you had a good eye and a steady hand. But then you still have to get them onto the reel. I never had the nerve; I think my hair would fall out in clumps if I tried.
View-Master was one of the very few companies who put out more than one stereo camera, they made a Personal and what is called a Mark II. Mine is the former.
Camera manual: Orphan Cameras.com
Modern Photography magazine special report: August 1955