So, I cut them, keeping the outside leg seams for simplicity's sake.
Then I used an existing pair of shorts to figure out a pattern. I added a waistband made from a fleece pullover I've had since 10th grade. (You know how I know it's that old? Angela and I bought matching ones from American Eagle before anyone shopped at American Eagle. I remember wearing my XL gray pullover to work at O'Charley's.)
I sewed up the crotch and legs, threaded some elastic through the waistband, serged it all together, hemmed them up, and called it shorts.
Lee liked them, and the fit was close to perfect. These were my test pair. I've got plans for more with some tweaks like a faux fly, adjusted elastic placement (to the center of the waistband), pockets, and a faux drawstring. If I'm feeling frisky, it may turn into my very first tutorial.