Heat a large, deep skillet over medium heat. Add the remaining 3 tablespoons of olive oil and saute the garlic for 1-2 minutes, just until it begins to turn golden. Whisk in 3 tablespoons of flour, and cook, whisking, for 30 seconds. While whisking, pour in the almond milk, 1/2 cup at a time. Stir in some salt and pepper. Lower the heat to medium-low, and continue cooking, whisking frequently, until the mixture thickens. Whisk in the nutritional yeast, if using. If the sauce seems too liquid-y, whisk in an additional tablespoon of flour. (For an extra creamy sauce, use an immersion blender to blend it at the end.) Stir in the lemon juice. Taste, and add more salt and pepper if needed.