It's a bit like a lecture this time.
"I'd be happy if you could just look at it like, "Oh, so that's how you do it.
Use a commercially available 3D model or self portrait as a base and draft in straight lines!
This will make it easier to draw natural poses and muscles that adhere to the minimum body proportions.
Then you can freely direct the drawing with straight lines on top of the model to make it more manageable.
2, "Direct as you like! is important!
The reason is that if you don't direct "like" well, you can replace it with another person's work.
After this, I draw details and add pen.
Main reference materials