First off you need to measure yourself, you need your waist measurement, your hip (round the biggest part at your bum), the length from your waist to where you want the flat panel to end then from the bottom of the panel to the bottom of the skirt.
Next you need to draw your pattern. Take your waist measurement in inches and add 4 (in my case that's 34 inches + 4) and divide it by 2 (19 inches). Take your drop from waist to hip and add 2 inches (for me it was 8 inches + 2). Last off take the hip measurement and add 4 (40 +4 for me) and divide by 2 (22 inches). Decide if you want to do a straight or curved shape (I did straight as I'm lazy and not so curvy). Also because I'm lazy and it is less complicated I made my pattern shape to be cut on the fabric fold. So that's the front of the skirt. If you have a fairly flat bottom then cut this shape twice, if you are slightly more prominant in the posterior then for the back or the skirt add a bit of a curve to the bottom of the pattern so it hangs down slightly in the middle once you cut on the fold.
That's the tricky part over, the rest of the pattern pieces are basically rectangles. The ruffle is entirely up to you, I recommend at least twice the width of the full hip measurement to get a bit of full on rufflyness.
Making up............. with right sides together stitch one side of the front panel to the back panel. At the other side add the zip and close the remaining length of the seam. Add the waist band (there's plenty tutorials out there to show you how). So now you have what looks like and extremely short skirt.
Next up make a very large tube from your fabric for the ruffle and hem the bottom edge. On the top edge make gather stitches until it measures the same circumference as the bottom of your teeny wee skirt bit and with right sides facing stitch together making sure your ruffles are even.
Check the post below for the finished result.