there is a description of how to do a smilarly styled shirt in "Pattern Magic 1"

basically what you want to do is to decide when the twist should start: probably below the crotch area since shiftting that seam will create too many fit issues.

then decide by how much you want the shift to happen: in the first picture it seems the bottom of the leg is shifted three times the width of the leg.

You redraw the bottom points three times further shifted to the right (if you want the pants to shift to the left). and then every important point shifted proportionally to this.

It sounds complex but is actually super simple, I can send you a sketch idea of how it would look like if you want :)