It seems pretty clear in the video. I created a reference plane corner-to-corner using the front plane and one corner to create a plane 45 degrees to the front, pivoting about the selected edge of that corner. Then I offset that plane using it to create another reference plane by entering the distance to the back of the boss on the top. I'm not sure what I could say that would clarify that, so I hope this helps.
Some printer noise in the background. Sorry about that, but I needed to get this done for a class and I didn't want to interrupt the print.
Please can you explain how you made the first plane?
It seems pretty clear in the video. I created a reference plane corner-to-corner using the front plane and one corner to create a plane 45 degrees to the front, pivoting about the selected edge of that corner. Then I offset that plane using it to create another reference plane by entering the distance to the back of the boss on the top. I'm not sure what I could say that would clarify that, so I hope this helps.