1/4 cup olive oil, plus more for serving 3 medium garlic cloves, smashed and chopped 2 small shallots, thinly sliced 1/4 teaspoon red pepper flakes 24 littleneck clams 1 pound spaghetti 1 cup chopped flatleaf parsley 1/4 cup chopped basil 2 teaspoons finely chopped preserved lemon rind 1 lemon, halved