Brilliant corners. How do you cut them?

So, like many here I managed to sort out a lockdown project, namely a 5E3. I've practised my tolexing already with a FET Reverb, but I need to raise my game and get brilliant corners.

Like these corners below - specifically the 90 degree corners on each edge of the control panel

How do you folks do them?

Fortunately I kept the sharp edge in the middle of the roundover (if that makes sense). But how do you select exactly where to cut?

This seems to be one aspect I've not seen on Youtube etc etc etc. All advice on cutting corners appreciated. I used a scalpel which I think was a mistake, a one-sided sharp razord blade kind of rotated on that sharp edge might work. But what are the tricks to get it neat?

(PS I don't mean the internatl bend, where we add the little extra triangle, which wasn't too hard, I mean the corner on the far left int the first pic, at where the control panel recess meets the back side of the amp).

Also, there's this supernatural vintage example at the bottom that seems to have no cut line. I can't begin to see how this was covered. Ideas?

 

I repeated this question to jsnwhite in his 5F11 thread. I thought I'd paste his answers in here, just in case anyone else is googling for the same issue.

 

I do love that album.

One of my key achievements in life was a headline for a magazine feature on Leonard Cohen, a story where he talked about his stealing ideas for songs, and his time in a monastery. It was titled "Felonious Monk."

For more brilliant corners, here is a really good discussion on Dunehunter's thread, with great examples from axis29 and jsnwhite.

btw, in my covering so far, I've already learned from muchxs, even though my scalpel blades are super sharp, they're too flexible compared with a new Stanley knife blade, which seems to have much more inertia, due to the weight, and is much better for straight-line cuts.