There are numerous ways to approach the objective. Like Bob, I don't think I'd suggest the method shown in the video, since it appears his jig is attached to the router, and the router is just sitting on the floor, wobbling back and forth. One slip, and his fingers will be in the bit, and the workpiece will be stained blood-red.
My preference would be a jig that holds the workpiece firmly in place, and then defines limits for the travel of the router, with the router being on top, so you can see what is being done. The task of defining the horizontal travel of the router could be done with either a template arrangement (with bearing-equipped bits or guide-bushing guides), or via stop blocks against which the router base would ride at the limits of travel. Either approach (template or stop blocks) would work.
The template approach would add a vertical depth-of-cut issue, particularly if limited to a bearing-equipped bit, since the template would need to be thick enough to provide a surface for the bearing to ride against for the entire depth-of-cut range.
The design of the jig, of course, depends on how you prefer to approach the cut, and how often you'll be using the jig.