These are super easy to make. I altered an Easy McCall's Pattern (5813) , but you can create your own pattern from a pair of pants that fit well in the waist and crotch, if you're skilled like that.
Lay out your fabric, folded in half. Place your pattern pieces, making sure the fabric pattern is orientated properly if it has a print that only makes sense in one direction. Pin the pattern to the fabric or use pattern weights to keep it in place.
My pattern has a front and a back for each leg, but it will work if you have a pattern that has only one piece per leg.
The fabric I used was finished along the edges, so I didn't have to hem them. If yours isn't, remember to add an extra half inch for a seam allowance.
The pattern had straight legs, so I added an equal width to each side of each pattern piece. I chose 4", a totally arbitrary decision. If you want them fuller or skinnier, just change that measurement. If you are working with a single piece leg pattern, double that amount so that you have 8" on either side of each leg piece.
My pattern wasn't long enough, so I measured from 36" from the top of the pattern to the bottom and marked it (I derived the 36" from measuring my favorite pins from just under the waistband to the hem. Again, if you need to hem the bottom, remember to add that half inch seam allowance!
Mark from the crotch to the new diagonal and from about the same distance from the top to the new diagonal on the other side.
My.pattern had one piece that was slightly longer than the other. If yours is like that, just ease them together as you pin. (Note to our intrepid news: "easing" is evenly distributing the length of one piece along The length of a shorter piece.)
With right sides together, pin front piece to back piece along the outside of each leg and see along the entire length. If you have to ease at all, it's easier to do with the longer side face down. The feed dogs distribute it more evenly than the presser foot. (I just learned that as I was making the first pair of these.)
I like to make a second stitch for all my seams super close to the first one, just outside along the seam allowance for extra durability. I get tired of repairing stuff after washing it a few times. It's totally optional, but highly recommended when you get to the crotch. Unless you have super cute underwear you want to eventually start showing off.
Pin the inside seam from the bottom tip of the crotch to the bottom edge and sew. Don't sew the crotch area yet.
Now comes the first of two easy parts that might confuse you. I always have to think carefully about these things when I haven't done them for a while, but I get turned ed around easily. You might not have that problem.
Turn one leg inside out and slip it into the other leg, matching the crotch curves. Pin and sew the crotch.
You'll end up with this.
Pull the legs separate so that they are both right side out. This is what it should look like.
Woot woot! They are starting to look like pants! Damn, you're gonna be looking fly!
Now, for the waistband. You can do a regular elastic and or drawstring yoke, but I'm fond of the fold over yoga waistband. If you want that kind, you need a t-shirt or some stretch fabric. I like the t-shirt because it gives you a finished edge and that's one less step. More time for getting distracted by Pinterest. (SQUIRREL!)
Draw a horizontal line 6-8 inches front the bottom of your t-shirt, depending on how wide you want the waistband. If you aren't using a t-shirt, add a half inch seam allowance. Cut along the line, then cut one side of the tube, so you have one long rectangle.
If you aren't using a t-shirt, hem one long edge using g a zigzag stitch to maintain stretchiness.
Measure your hips where you want them to sit. Subtract two inches (or more, if the fabric is super stretchy). Cut the rectangle to that length. Sew ends together, making sure the wrong side of your hem is facing out. You should now have a tube again.
Here is the next easy part that may trip you up if you are daydreaming like I always do. Flip the tube right side out and tuck it into the top of the pants with the raw edge running along the top of the pants and the hemmed edge hanging down inside the pants. Pin raw edge of pants to raw edge of yoke, matching the yoke seam to the back of the pants and the finding the spot on the yoke just opposite of that, pinning that, then doing the same thing to the sides. Sew yoke to pants using zigzag stitch to allow stretch. Don't tug on fabric as you sew. Tugging causes ripples in the seam.
It should look like this.
Fold the waistband down like this.
Guess what! You're all done! Go put them on and check out how fabulous you look!