Hand cut with either chisel, and router plane or saw and then pare and route. I avoid the line move by using a knife line and the pare the waste leaving a groove dead to knife line.
Yeah, I did think about the router, as I was pushed for time, I thought it would be quicker to use the saw as it is always set up. Even though, with the router to cut housings you need to set up the router and jig and then clamp it for every housing, and these are simple housings, not stopped on moderately narrow board so the saw can handle them with ease and on this occasion faster than the router set up. Though it does really depend on what tools you have available to you, which I think is an important part of the video. More than one way to skin a cat as they say!
