Fold your pants

As with shirts, the secret to flat, neatly folded pants lies in lining up the seams and hems of the pants.

Hold pants by the waist and flap up and down several times to smooth out large folds. Lay down on folding surface so that the seams from each pant leg are parallel.

Pull gently on those seams until they're slightly taut.

Now you have two options. If you stack your pants in a shelf or drawer, fold your pants in thirds as shown in the diagram. Hanging the pants on a hangar requires only a single fold in the middle of the pants.
Congratulations! You have acquired the skills (well, some of them, at least) to re-enter the world in cleanliness and in style.