I finished previous post about my first down jacket at a stage where I had patterns and marking templates ready. What was the next challenge, let me remember..
Next several steps are pretty straight forward: cut all fabric pieces; mark all stitching lines on the face pieces (I mark with a fine pencil, so after stitching marking is invisible, though I work so far with black fabric only, I'll have to rethink it if working with light colors); connect two pieces comprising a same finished piece, let's say face and inside of left front bodice piece, along any edge that would not be connected with any other part in finished garment (if it would be collarless west, for example, I would have joined front bodice pieces along the hem, armscye and collar line); turn inside out and press; stitch along marked lines; stuff with down, stitch close openings through which you were stuffing and proceed connecting pieces together like you would have in a regular garment.
And here you are, wearing a down jacket that fits your needs:
There is a lot of specific requirements and limitations when making a down garment, I'll dedicate a separate entry to this topic once I have enough experience to share.
UPDATE: Augut 27, 2019
Check out the stuffing process for down garments in my video tutorial: