Blanch the green beans. Preheat an oven to 450°F / 230°C. Bring a large pot of water (at least 2-3 quarts) to a rapid boil. Submerge the string beans into the boiling water. Cook for exactly 3 minutes, then transfer to a prepared ice bath. Cool for 5 minutes before draining. (Can be prepared 1 day in advance, then refrigerated.)
Parboil the potatoes. Return the large pot of water to a rapid boil. Add 1 Tbsp Kosher salt and ½ tsp baking soda. Carefully add the potatoes, then cook for 10-12 minutes. Drain, then return the potatoes to the warm pot, seal with a lid, then hold in place with pot holders and shake vigorously for 15-20 seconds.
Roast the potatoes. Drizzle 2 Tbsp olive oil on a rimmed baking sheet, then pour the potatoes on top. Use your hands or a spatula to spread into a single even layer. Cook for 40 minutes, flipping the potatoes once halfway through cook time.
Make the dressing. While the potatoes cook, make the dressing. Combine ½ cup extra virgin olive oil, 2 Tbsp fresh lemon juice, 1 Tbsp chopped oregano, 1 Tbsp thinly sliced chives, 1 clove chopped garlic, 1 tsp honey, 1 tsp Kosher salt, and ¼ tsp black pepper in a mason jar. Seal tightly, then shake until well mixed. Alternatively, you can whisk dressing ingredients together in a small bowl.
Assemble the green bean salad. When ready, place blanched green beans on a large platter. Top with crispy potatoes, ¼ cup thinly sliced red onion, ⅓ cup halved Kalamata olives, and ⅓ cup feta cheese. Drizzle the dressing on top, then serve immediately with additional chives, if desired. Can be enjoyed warm or room temperature.