I used my basic long sleeve sloper to draw the initial shape, then I added tons of volume by slashing open the seams. I wish I could go into details but you know... trade secrets!!
Now it's time for the sample to test out the shape. I use a less popular jersey fabric I bought a few years ago to make the initial sample. My boyfriend has hated this fabric color since the day I got, he's always said it looks like pyjama fabric. My first sample (below) didn't have enough volume at the neckline so it's back at the drawing board to slash some more.
My second attempt was a success and I was able to sew it up in my bamboo jersey in my new shade of grey/taupe. In some cases, I'm not so lucky and I end making a few samples until I get the perfect shape.