Preheat oven or toaster oven to 450 degrees. Split baguette lengthwise and lightly brush cut sides with 2 teaspoons olive oil. Bake until golden around edges, 5 minutes. Meanwhile, in a small bowl, mash together feta, 4 teaspoons oil, and lemon juice with a fork. Season with salt and pepper. Spread feta mixture evenly over toasted baguette and top with cucumber. Season with salt, pepper, lemon juice, and a drizzle of oil. Cut into pieces to serve.