01 - Set oven to 425°F and line a large baking sheet with parchment paper.
02 - In a large bowl, combine halved Brussels sprouts with olive oil, sea salt, black pepper, and chili flakes if using; toss well to coat.
03 - Place Brussels sprouts cut side down in a single layer on the prepared baking sheet.
04 - Roast for 20 to 25 minutes, stirring once halfway, until edges turn crispy and deep golden brown.
05 - Remove from oven, immediately drizzle with honey and apple cider vinegar, and toss to evenly coat.
06 - Transfer to a serving dish, sprinkle with toasted sliced almonds if desired, and serve hot.