In a large bowl, combine 8 cups of water and ½ cup salt. Pour in halved Brussels sprouts and allow to sit in brine for 20 minutes. Preheat oven to 400 degrees F. After 20 minutes, drain and pat dry. In a large bowl combine Brussels Sprouts, 3 Tbsp olive oil and black pepper, toss to combine. Spread Brussels sprouts evenly on sheet pan with cut side down. Place in oven to roast for 25-30 minutes, flipping once halfway through.
While Brussels sprouts are roasting, make the glaze. In a small bowl, combine honey, mustard, olive oil and red pepper flakes if you desire, whisk until mixed well. The Brussels sprouts are done when you can pierce a fork through the center and the outside leaves are crispy. Remove from oven, place on serving platter and drizzle with glaze to taste. Enjoy!