Heat the extra-virgin olive oil in a deep skillet over medium-low heat with garlic and anchovy. Cook together 3 to 4 minutes to infuse garlic into oil. Remove the garlic cloves and stir oil to mix in the melted anchovies and add the red pepper flakes. Raise heat to medium-high. When oil ripples or begins to waft smoke, add greens and stir fry them 2 to 3 minutes. Squeeze lemon juice over the greens, toss, and serve.