Line a baking sheet with several layers of paper towels. Cook the green beans in a large pot of boiling salted water until crisp-tender, 4 to 6 minutes, depending on size of beans. Drain. Spread beans out on paper towels. DO AHEAD: Can be made 2 hours ahead. Let stand at room temperature.

Combine pancetta and 1/2 Tablespoon oil in large nonstick skillet. Saute over medium heat until pancetta is crisp, separating pieces with 2 forks, about 10 minutes. Add sage and stir until fragrant, about 1 minute. Transfer to plate.

Heat remaining 1/2 Tablespoon oil in same skillet over medium-high heat. Add beans and saute until heated through, about 5 minutes. Add pancetta mixture and toss to blend. Season to taste with freshly ground black pepper. Transfer beans to large bowl; sprinkle with sea salt, if desired, and serve.