How do we do it? Stair railing

[Therese Viklund]

We are building a new stair railing for the first time in our lives. What are we not considering? No matter how we cut, the lower part is too high.
How should piece 1 be cut, that is, the small piece, and then the remaining bottom of the stair railing?

 

[Fotografen]

You must miter the corner in the middle of the angle, otherwise the cuts will be of different lengths.
https://www.byggahus.se/forum/threads/kapa-hoern-pa-altandel-hjaelp-med-grader.117377/

Example: