Preheat the Oven: Begin by preheating your oven to 425°F.
Prepare and Roast the Leeks: Arrange the sliced leeks on a large rimmed baking sheet. Drizzle with ¼ cup of olive oil, sprinkle with 1 teaspoon of kosher salt, and season with the black pepper. Toss the leeks until evenly coated, then roast them for about 20–25 minutes, stirring occasionally, until the edges are crisp and the color is golden brown. A few blackened bits are fine—they enhance the flavor.
Combine Leeks and Chickpeas: Transfer the roasted leeks to a large mixing bowl. Add the chickpeas, lemon juice, remaining teaspoon of salt, chile flakes, and grated garlic. Stir in the remaining ½ cup of olive oil. Let the mixture marinate while you cook the farro.
Cook the Farro: In a large pot, bring salted water to a boil. Add the farro and cook until tender, approximately 20–25 minutes (some varieties may take longer, so taste to check for doneness). Drain the farro thoroughly once cooked.
Assemble the Dish: Combine the cooked farro with the marinated chickpea and leek mixture. Mix in the dried currants and chopped celery leaves. Taste the dish and adjust the seasoning with additional lemon juice or salt if needed. Serve warm or at room temperature.