I hear a lot of plus ladies get really nervous when it comes to wearing pencil skirts. If you want to wear a pencil skirt and create clean lines most likely you will have to tuck your top in and some get nervous about the tummy area. What I say to that is if you pick a good fabric with a nice weight then the skirt will be more complimentary to the areas that you want to compliment.
The skirt I'm wearing is made of a nicely weighted scuba (aka neoprene) fabric. Scuba is one of my favorites and it makes everything look smooth and snatched. LOL! Other fabrics I like for pencil skirts include ponte knit, stretch sateen, and stretch twill. If you are having issues finding a pencil skirt that looks good on you, I would steer clear of the jersey knit pencil skirt. A lot of pencil skirts come in a jersey knit. Although I wear skirts in the fabric too, they aren't very forgiving and have a tendency to be very thin.
Style Notes: I always get asked about my shapewear. I just purchased a new one recently from Spanx. You can find it here (I will also link it at the bottom). I purchased this skirt in a size 24. The top was purchased in a size 0 (or 12). That's not my normal size, but it looked like it would stretch and ended up working out. You'll want to note that the top is a peplum top and I tucked it in.