Hip beams in a hipped roof, always a nightmare... :-)

Hi.

I am trying to get that of the attached sketc, but the closest I get can be seen on attached pictures.
Why the bottom of the hip beam is not horizontal? Is there any ways to make what I want? It would be nice if it was possible to simply put in a completely rectangular piece of wood in the hip line, as you can in the ridge line.

Interesting suggestion - I did try anything else than plates. I will give that a try! ...