I've been piecing my muslins from a bunch of 1/2-3/4 yard cuts my friend's roommate left behind when she moved (apparently she did some kind of theatrical sewing)--it's mostly muslin but some of it might have been pillowcases at one time. I made sure to match the grainlines on each piece, which makes a HUGE difference in how the garment hangs. (Dear self five years ago, it does so matter, I'm sorry, you were wrong.)
I usually cut a paper pattern with no seam allowances, and trace around it right onto the fabric. I know some people thread-trace the grainlines and horizontal fitting lines but I don't have the patience for that--I just use whichever marker comes to hand first, which today was pink.
...no drag lines! I don't intend to stand like a sailor at all times though so I need to fix this problem.
For the second muslin, I hinged out the inseam at a wider angle (technique helpfully illustrated at #2 here), a couple of inches out at the hem tapering to nothing at the fork. I also gave the inner thigh portion of the inseam a slight convex curve, which hopefully will relieve strain on the fabric in that area and keep the pants from wearing out quite as quickly (that's the first place my pants always get holes). First impressions are good:
There's some wrinkling around the crotch, but well within acceptable levels IMO. Grain lines and side seams are approximately perpendicular to the floor, nothing's obviously out of whack--there's a little too much room from the knee down but we're going to do something about that now.
First I tried pinning out a vertical dart along the crease line (center grainline), tapering to nothing at the knee:
That did not work. It was weird. As soon as I took a step, the leg started twisting inward from the knee down, a problem I had with the last pair of jeans I made and never figured out. I still don't understand what caused it, but it was immediately obvious that no matter how big my calves are, the solution is not to make the front narrower than the back.
Second, I tried pinning out the excess along the outer seam, which I suspected was going to be the best solution (and a test of my inward-angled-leg theory). And it worked! It worked so much!
I got a little overzealous and pinned out too much at first, but once I let the pins out slightly into a more gentle taper, it was perfect. Minimal twisting, and comfortable! I like to wear a muslin around the house for a while before I make a final decision, just to make sure I can, like, bend over to get into the dishwasher, or curl up sideways on the couch and watch TV. And I can! The final fabric is going to be a woolen with a bit of give to it and stretch silk underlining, so these should be very comfortable when they're all done.
Lastly, I bring you a picture of my butt.