Preheat your oven to 425°F (220°C). Line a large rimmed baking sheet with aluminum foil for easy cleanup.

Spread the bacon pieces in a single layer on the prepared baking sheet. Roast for 4–5 minutes until just starting to render but not yet crispy. Remove from oven.

While the bacon renders, trim the stem ends off the brussels sprouts and halve them lengthwise. Pat completely dry with paper towels — this is critical for crispiness.

In a large bowl, whisk together the olive oil, 2 tablespoons of the maple syrup, apple cider vinegar, minced garlic, salt, pepper, and red pepper flakes if using.

Add the halved brussels sprouts to the bowl and toss thoroughly to coat every surface in the glaze.

Spread the glazed brussels sprouts cut-side DOWN on the baking sheet with the partially rendered bacon, distributing everything in a single uncrowded layer. Do not overlap.

Roast at 425°F for 18–20 minutes until the cut faces are deeply golden-brown and caramelized and the bacon is crispy. Do not stir — let the flat faces caramelize undisturbed.

Remove the pan from the oven and drizzle the remaining 1 tablespoon of maple syrup over the brussels sprouts. Return to the oven for 3–5 more minutes until the glaze is bubbling and lacquered.

Remove from oven. Taste and adjust salt if needed. Transfer to a serving platter and serve immediately.