I wear a pair of sweatpants under jeans, a pair of woolsocks over kneehigh tubesocks, 4 layers of thermal shirts, underarmour xl armored hoodie, refidgiwear bibs and jacket, and insulated boots.
I work in a -20f freezer on standup forklifts and can stay there for 5hours or more if I wanted to. one tip would be to make your outer layers a larger size as you build out. I can wear a large t-shirt but by the time i get to my outer bibs and jacket, im up to a 3XLT. you can build up less than what I have and still be comfortable in 10-15f