Make the vinaigrette: Whisk together 0.3 cups olive oil, 2 tablespoons fresh lime juice, 1 tablespoons maple syrup, 2 tablespoons fresh mint, finely chopped, 0.8 teaspoons salt, and pepper to taste until fully combined. Adjust seasoning as needed. Set aside.

Toast the hazelnuts: Toast 0.3 cups toasted hazelnuts in a dry skillet over medium heat, stirring frequently, until golden and fragrant. Cool, then roughly chop if desired.

Prep salad ingredients: Dice 1 avocado, diced into bite-sized cubes. Slice 1.5 cups cucumber, thinly sliced into thin rounds. Wash 5 cups arugula, 1 cups blackberries, and 0.8 cups blueberries. Crumble 0.3 cups feta cheese.

Assemble the salad: Add 5 cups arugula to a large bowl. Top with 1 cups blackberries, 0.8 cups blueberries, 1 avocado, diced, and 1.5 cups cucumber, thinly sliced. Scatter over 0.3 cups feta cheese and 0.3 cups toasted hazelnuts.

Dress and serve: Pour vinaigrette over salad and toss gently. Serve immediately. If prepping ahead, add dressing and avocado only just before serving.