Thinly slice the radishes and cucumber, keeping their skins intact. Use a vegetable peeler to slice along the length of the asparagus, creating thin ribbons. Add the radish, cucumber and asparagus pieces to a salad bowl. In a separate, smaller bowl, whisk together the oil, vinegar, lemon juice, maple syrup, salt and pepper. Pour over the vegetables and toss until all ingredients are combined and the dressing is coating all of the pieces evenly. Top with crumbled feta cheese and give the salad one last light toss. Serve with a dash of red pepper flakes. Enjoy!