Layer your salad into your mason jar in the order of ingredients: dressing, sunflower seeds, pumpkin seeds, sliced almonds, shredded chicken, Brussel sprouts, and baby spinach.
Notes
To make the shredded chicken, see this post on how to make the perfect chicken breast.To make the roasted Brussel sprouts, coat with olive oil, salt and pepper, and roast in a 400F oven for 15-20 minutes.