Well firstly I never sewed clothing before so I started with a fleece vest.
I looked for a pattern that looked as much as this one as possible and ended up using
https://wardrobebyme.com/collections/mens-pdf-sewing-patterns/products/fleece-jacket-sewing-pattern
A friend edited to use no stretch fabric.
When you have you’re pattern complete
1 I’ve made the inner shell first. So I had a complete jacket in red (but without zipper and such) so I could test the fit.

2 stitch all apex parts to the outer shell pattern pieces.
3 sew all shell pieces together.
4 sandwich the “jackets” rights facing with the inner on the outside.
5 create a sandwich to create the zipper and draft stopper. From bottom to top : outer – zipper with teeth down facing away from the seam – draft stopper – inner.
6 sew everything together and flip it. Leave a small gap on the inner. Under the arm on the hem and sew that by hand. There are lots of yt videos on how to do so.
And that’s about it. To make the sewing easier on such thin fabric u used water soluble tape to tape it together and sewed over the tape. Made a perfect stitch and doesn’t shift on you. Then a hand wash and it gone. Just a tip.
Hope this helps?