Pattern (this is folded, I would iron it out to make it more flat if I was going to use it):
You might want to take apart a pair of pants that fits you to make a pattern.
You cut out two identical pieces. Actually mirror images but both sides of supplex are identical so it doesn't matter.
You sew the two pieces together at the top. Front and back. Use a French seam.
Then sew them together on the inseam with a french seam. Voila! you have a pair of pants!
I am always amazed at the topology that this produces a 3 dimesional pair of pants.
Sew on pockets.
Hem the bottom of both legs if you're doing shorts, make an elastic sleeve if you're making pants and put in elastic.
Put a sleeve in the top. I use both a piece of elastic and a nylon cord. The elastic holds the pants up if I don't have anything in the pockets, the nylon cord is needed if I'm carrying weight in the pockets.
I should write up a more detailed description that's easier to follow.