I make pleated skirts all the time without a pattern. The first time I made a box pleated skirt, I made a trial run with paper (to figure out the width of the pleats and how much fabric I'd need to go around completely).
Do your hem first though! That way you can iron it down with your pleats. And make sure your waistband is long enough for your fasteners.
IKKiCON VIII, All-Con 2014, A-Kon 25
Kayle (IntoxicatedPeng) - Drocell Keinz (Kuroshitsuji), Yuki Onna (Nurarihyon no Mago), 8th Doctor (Doctor Who), Soul Eater Evans (Soul Eater), Lucy (Fairy Tail) - Also attending Gallifrey One 25
Mara - Lulu (FFX), adult Nel (Bleach), Hagoromo Gitsune (Nurarihyon no Mago) WITH Baby Moogle, Trystan
Me - Mary Poppins, The Woman (Doctor Who, The End of Time), Sibylline Sisterhood (Doctor Who)