Preheat the oven to 400°F. Line a rimmed baking sheet with heatproof parchment paper for easy cleanup.
Make the sauce: In a small bowl, mix the oil, soy sauce, honey, garlic, and red pepper flakes.
Place the Brussels sprouts in the pan and toss them with the sauce.
Arrange the seasoned Brussels sprouts, cut side down, in a single layer on the baking sheet.
Roast them, undisturbed, until browned and caramelized, for about 30 minutes.
Taste and decide if you'd like to sprinkle the dish with kosher salt. To my palate, the soy sauce makes it salty enough. Garnish with sesame seeds and serve.
Video
Notes
If using sugar-free honey, each serving has about 12 grams of carbs (excluding sugar alcohols) and 5 grams of fiber.
To promote crispness, the sprouts should be as dry as possible. This is a good reason to use bagged pre-washed sprouts that don't need washing.
There's no need to flip the sprouts midway. Allowing them to roast undisturbed ensures that the side that touches the pan becomes browned and caramelized.
Oven temperatures vary. Start checking the sprouts after the first 20 minutes.
I don't recommend using frozen sprouts. They won't crisp up as well and might end up mushy.
You can keep the leftovers in an airtight container in the fridge for 3-4 days. Gently reheat them in the microwave, covered, at 50% power, or (uncovered) in a 350°F oven. You can also freeze the leftovers for up to three months.