I recommend Draw a box! it's how i got better at elipsies
I found it to be really helpful to go through most if not all of their lessons
https://drawabox.com/lesson/1/ellipsesinplanes
Personally I tend to think of the torso as 2 boxes, one for the chest and one for the stomach area and I angle/twist the rectangles accordingly then connect the dots so to speak, like so:

I'm not that good at it yet but it works :3
hope that helps! 