Trim and cut the green beans into 1-inch pieces, then set aside. Zest the lemon into a small bowl (you'll need about 1 tablespoon), then cut the lemon in half and juice it to get 3 tablespoons of fresh juice—set the juice aside separately. Mince the garlic clove finely. Bring a large pot of salted water to a rolling boil; this will be your cooking base for both the pasta and beans. While the water heats, I like to have all my ingredients measured and prepped so there's no scrambling once cooking begins.
Once the water is boiling, add the pasta and cook for 10-12 minutes according to package directions, stirring occasionally to prevent sticking. About 2 minutes before the pasta finishes cooking, add the prepared green beans to the pot so they finish cooking together. The pasta should be al dente with a slight bite, and the beans should be tender-crisp. Drain everything into a colander and rinse with cold water to stop the cooking process and cool the pasta quickly.
While the pasta cooks, chop the mixed fresh herbs (basil, parsley, and mint) into bite-sized pieces and place in a large serving bowl. In a small jar with a lid, combine the 3 tablespoons of fresh lemon juice from Step 1, the extra virgin olive oil, minced garlic, kosher salt, freshly ground black pepper, and crushed red pepper flakes. Cover the jar tightly and shake vigorously for 30 seconds until the dressing is well emulsified and the flavors begin to marry together.
Transfer the cooled pasta and green beans from Step 2 to the large serving bowl with the chopped herbs from Step 3. Pour the prepared dressing from Step 3 over the pasta and toss everything together gently but thoroughly, making sure every strand of pasta is coated with the bright, herbaceous dressing. I find that using tongs or pasta servers helps distribute the dressing evenly without breaking the pasta.
Taste the pasta salad and adjust the seasoning with additional salt and pepper if needed—remember that the cheese will add saltiness, so be conservative. Just before serving, top the pasta salad with the freshly grated pecorino cheese and the reserved lemon zest from Step 1, which will add a bright pop of citrus flavor and an elegant finish.