So here goes... This is my first tut and I could only do it using these crappy paint drawings, but this was somewhat easy so hopefully it will help!
These are the pieces: the long straight ones are for the bottom band of the halter, the small straight ones make the bow on the front of the bottoms. The triangly ones are the cups and neck tie for the halter and the big pieces are the bottoms. These last 2 you will want to modify for your own size.
All of the pieces for the top, and the bow are sewn like a pillow (with the pieces facing eachother) and then reversed- the inside and outside will both look the same once it is assembled (you could even use 2 different fabrics and make it reversable!)
I made the bottoms like a pair of short shorts that were a little too big and then added the elastic around the waist and legs to cinch it in and give it that puffy vintage look. I also added elastic on the side of the bra cup near the armpits to keep my boobs from hanging out the side. The "bow" on the bottom also helps tighten it a little when you tie it in the front(not a real bow, but a knot)
Before sewing the triangles into the band I put the bra cups in (I just took pads from an old bra that had removable ones, but you could get new ones at a fabric store)
Then I just added the ruffles around the leg and on the inside front of the halter.
Hope its not too confusing!