Can the 12 inches off the legs. If you want, you can make it shorter later.
Rip the seams with a seam ripper. To do this you’ll have to turn the pants inside out and rip the seams at the crotch and go all the way down both of the inseams.
Now you have to rip the front seam up to where the zipper begins and rip the back seam up to where your belt loops begin.
Pin the front pieces together.
Then, turn your skirt inside out and pin the back pieces together.