Heat oven to 350°F. In a bowl, whisk 5 teaspoons olive oil with 5 teaspoons pure maple syrup and 1/4 teaspoon cayenne pepper. Stir in 1 tablespoon chopped fresh rosemary and 2 teaspoons chopped fresh thyme. Add 2 cups walnut halves; toss well to coat. Spread evenly on a baking sheet lined with parchment paper. Bake until fragrant and crisp, 10 to 12 minutes. Sprinkle with 1 teaspoon chopped fresh thyme and 1/4 teaspoon kosher salt. Cool completely.