From FibreMood:
Show them you’re a goddess. Ulla's simplicity will turn every head in the room. This fluid calf-length halter dress has a slightly fitted bust and gently flows at the bottom. The necklines of the front and back feature gorgeous draping. A lovely wave effect is created by threading a cloth tie or cord through the neckline's casing. Add your own personal touch, perhaps a cord in a contrasting colour, a lovely bow with long trailing ribbons, a delicate string of pearls? This understated dress isn't hard to make, and it’s always stunning whatever length you choose.
Fabric advice
Ulla can be made in a woven or a knit fabric, but whatever you choose must have a fluid drape. Stiff fabrics (e.g. thick denim) with no drape will not give you that lovely undulating effect.