90 degree tube notching method without a drill press.

[Baddog]

If you search "chop saw tube notching", there are lots of examples out there. The one I first saw provided by tigweld is very simple and straightforward.

This is a post I made years ago, and it references the original tigweld post.

I've used the template approach before, but I like this because with a single print out you can quickly make cuts with many different intersecting angles. I don't actually use a chop saw most of the time due to noise and mess. And as you say, lots of different ways depending on goals, project, and tools available. It's always good to have a selection of ways to do something.