1. Place zucchini, cut side up, on a wire rack set in a rimmed baking sheet. Season with 1 tablespoon salt, flip, and let stand until slightly softened and juices are released, about 1 1/2 hours. Gently squeeze zucchini, extracting as much liquid as possible, and pat dry.

2. Meanwhile, preheat grill over medium-high heat. Brush zucchini with 2 tablespoons oil and grill, flipping once, until lightly charred and tender, about 15 minutes total. Transfer to a 9-by-13-inch baking dish.

3. Heat 1 tablespoon oil in a small skillet over medium heat. Add shallots and garlic and cook, stirring occasionally, until translucent, about 5 minutes. Distribute shallot-and-garlic mixture evenly over zucchini. Sprinkle with coriander seeds, huckleberries, and 1 teaspoon salt. Drizzle with vinegar and remaining cup oil. Marinate mixture at least 1 hour at room temperature or (preferably) up to 24 hours in refrigerator. If refrigerated, bring mixture to room temperature before serving.

4. Layer zucchini mixture and feta on a serving platter, drizzle with some marinade, and garnish with coriander sprigs and huckleberries.