Pencil-skirt lengthen and slit closure

Ever had a pencil skirt that was super cute but the slip went halfway up the back of your thigh? And when you sat down the skirt rose up like four inches?  Hey, me too!

So I took my favorite pencil skirt that I NEVER wear (EVER!) because of these problems,  and added a little length at the bottom and sewed a little triangle from a scrap of jersey cotton I had in my miscellaneous fabric drawer at the slit and VOILA! Usable clothing again. Hurray!

               

An up-close view of the pattern.