If you can follow pictures as well as a video, I have made two tutorials and posted here on the board. One is for the narrow joining method, and the other is for a wider sashing join, with batting inserted. They are here:
narrow joining strips:
https://www.quiltingboard.com/vbulle...l-t283918.html
wide sashing strips with batting inserted:
https://www.quiltingboard.com/vbulle...o-t304427.html
Good luck finding a video if that's what you still want.