Step 1: Video of Autodesk Sketchbook Pro LINK
This is my video of how used Sketchbook Pro!
Step 2: Thought Process!
Also these pants are no longer skinny jeans they are a mix of boot cut and bell bottoms!
I start the design process by thinking of what I want, then I draw out the idea. After that I do a math process so that I can cut the panels accurately. With me I usually end up making a few mistakes and having to rehash the math. If you were to do something similar make sure you do the waistband math correctly.
These jeans might suit bigger people, but it could also suit thinner people if they were to like the design/ idea.