Trim and cut: Trim the stem ends off 1.5 lb Brussels sprouts and remove any damaged outer leaves. Slice the sprouts in half lengthwise. Quarter any extra-large ones so the pieces are similar in size.
Soak and dry: Rinse the sprouts, then soak them in a large bowl of cold water for 10 minutes. Drain well and thoroughly pat dry with a clean kitchen towel, including between the leaves.
Preheat and season: Preheat the air fryer to 400°F for 5 minutes. In a large mixing bowl, toss the dried sprouts with the 2.5 tbsp olive oil, 1 tsp coarse sea salt, ½ tsp garlic granules, and 1 tbsp maple syrup until evenly coated.
Air fry: Add the sprouts to the basket and spread them out as evenly as possible. Some overlap is okay in a 6-quart basket. Air fry at 400°F for 10 minutes, shaking the basket or tossing the sprouts halfway through. The outer leaves should be browned and crisp, and the centers should be tender when pierced with a fork. If needed, cook a little longer, checking frequently.
Mix the sauce: While the sprouts cook, stir together the 1.5 tbsp maple syrup and 2 tbsp lemon juice in a small bowl.
Finish and serve: Transfer the hot sprouts to a serving bowl and toss with the maple lemon sauce just before serving. Taste and add more salt, if needed. Serve warm.
Notes
Soak, then dry well: The 10-minute soak helps the centers turn tender. Thoroughly pat the sprouts dry afterward so the surface can crisp during cooking.
Air-fryer size: This recipe was tested with the full 1.5 pounds in one batch in a 6-quart basket-style air fryer. Cooking time may vary with your air fryer and the size of the sprouts.
Oven option: Toss the sprouts with the seasonings as directed, then spread them on a baking sheet in a single layer. Bake at 400°F for 35–40 minutes, tossing occasionally, until browned and tender. Toss with the maple lemon sauce just before serving.