Put eggs in a medium saucepan, cover with 1 in. water, and bring to a boil. Immediately remove from heat and let sit 9 minutes. Meanwhile, whisk salt, pepper, vinegar, mustard, and oil together.
Transfer eggs to a bowl of cold water and let cool a minute. Crack gently all over, then return to water for 5 minutes. Peel and cut or break into quarters.
Put lettuce in a large bowl and toss gently but thoroughly with dill, chives, and most of dressing. Add eggs and gently toss again. Top with flowers if you like.