I made this asymmetric skirt using a simple standard pencil skirt pattern. (There are lots on Pinterest if you don’t have one – have a look at my Pinterest board of Free Sewing Patterns). I cut the front panel out of a very soft leatherette (Fabworks – £5 / metre) and the back is made from a glitter check that has a slight stretch in it. Perfect for a skirt like this as it fits and hangs nicely without clinging but has a bit of give in it for when you sit down.
Then I created the part-panel (just over half the width of the existing front panel). I cut 2 mirror pieces at an angle to create the asymmetric hem. You can make it more or less angled depending on how much of a statement you want to make. I sewed these 2 pieces together. (Right sides together and then turned the right way out for a nice finish – don’t forget to snip the corner off at a diagonal so you don’t get a bulky lump inside). If you are using a heavier material than this one, I would perhaps use one layer of your heavy fabric and back it with lining fabric to stop it getting too bulky. Then stitch your asymmetric flap onto the front panel across the top.