Preparation Cook green beans in a large pot of boiling salted water until just tender, about 3 minutes. Drain; transfer to a bowl of ice water and let cool. Drain. Place in a large heatproof jar or bowl with fennel and lemon slices. Bring chiles, vinegar, sugar, peppercorns, 2 tablespoons salt, and 2 cups water to a boil in a medium saucepan; pour over green beans. Let cool. Cover and chill at least 12 hours and up to 2 weeks.
Preparation Cook green beans in a large pot of boiling salted water until just tender, about 3 minutes. Drain; transfer to a bowl of ice water and let cool. Drain. Place in a large heatproof jar or bowl with fennel and lemon slices. Bring chiles, vinegar, sugar, peppercorns, 2 tablespoons salt, and 2 cups water to a boil in a medium saucepan; pour over green beans. Let cool. Cover and chill at least 12 hours and up to 2 weeks.