I cut two rectangles based on how wide I wanted the hem to be. For example, my hips are 33.5", so I estimated that I needed about 35" because I wanted it to drape loosely at the hip area. Divide that figure by 2, so you would need two 17.5inch by ___(how long you want your skirt to be)___inch rectangles. After that I gathered the top edges and pinned + sewed them onto the waistband. Let me know if you prefer an illustrated example
I'm not sure if this is the right way to do it, or if there's an easier alternative, so maybe you could ask around? But if you're comfortable with gathering and don't mind ripping seams out I'd say give it a shot! I'm a total sewing novice too and I did it in 3 days
Please post pictures!