Bring about 3 quarts of water to a boil and salt very generously (about 2 tablespoons). Add green beans and boil for 3 minutes, or until just tender but not mushy. Use tongs (or drain in a colander) and transfer to a bowl filled with ice water. Alternatively, drain them and submerge them in cold water in your sink. This stops the cooking process so they don’t get mushy (see video).
In a large bowl, add the oil, vinegar, paprika, salt, pepper, and feta. Whisk to combine. Add green beans and half of the nuts to the bowl and toss to coat. Taste and season with more salt, if needed.
Transfer to a platter or your plate, making sure to get all of the dressing, nuts, and cheese that fell to the bottom of the bowl. Top with remaining nuts, fresh herbs (if using), and a squeeze of lemon.