Kurt Vonnegut neatly describes the concept of slit scans in his novel ‘Slaughterhouse Five’:
“The Tralfamadorians can look at all the different moments just that way we can look at a stretch of the Rocky Mountains, for instance. They can see how permanent all the moments are, and they can look at any moment that interests them. It is just an illusion we have here on Earth that one moment follows another one, like beads on a string, and that once a moment is gone it is gone forever.”

With a traditional slit scan, the camera film is steadily rolled under a narrow slit such that each moment of time is captured from one end to the other. This technique creates interesting and unusual distortions in time.

I have used video editing techniques to endow myself with Kurt Vonnegut’s Tralfalmodorian vision: