Heat a large skillet over medium heat and add the almonds, toasting them for 4-6 minutes, stirring occasionally, until they turn golden brown and fragrant. Transfer to a bowl and set aside. While the almonds toast, mince the garlic clove very finely—this will ensure it distributes evenly throughout the dressing. In a separate small bowl, whisk together the olive oil, lemon juice, Dijon mustard, minced garlic, black pepper, red pepper flakes, and 1/4 teaspoon of salt to create the vinaigrette; set this dressing aside.
Return the skillet to medium heat and add the trimmed green beans, 1/4 cup water, and 3/4 teaspoon of salt. Cover the skillet and steam for 7-10 minutes until the beans are bright green and tender-crisp. I like to keep the lid on during this phase so the steam cooks the beans evenly without losing moisture. Once the beans are tender, remove the lid and increase heat to medium-high, cooking for another 2-5 minutes until all the water has evaporated—this concentrates the flavor and prevents the salad from becoming watery.
While the skillet is still warm, pour the dressing from Step 1 into the cooked green beans and toss well to coat everything evenly. Add the toasted almonds and half of the crumbled feta, folding gently to combine without breaking up the cheese too much. Transfer to a serving bowl or plates, then top with the remaining feta chunks. Stack the fresh basil leaves and slice them into thin ribbons, then scatter over the top as a finishing garnish. Serve immediately while the green beans are still warm—the warmth brings out the aromatic qualities of the basil and makes the dressing coat the beans beautifully.
For an optional finishing touch that adds brightness and visual appeal, finely zest a fresh lemon and sprinkle it over the top of the salad just before serving. This adds a pop of color and intensifies the lemony flavor without adding excess liquid to the dish.