Cut the cucumber into ½cm-thick diagonal slices. In a medium bowl, mix the cucumber with the flaked salt and the lime juice. Set aside to pickle while you make the rest, or for up to 1 hour. In a large bowl, cover the noodles with boiling water and leave for 5 minutes, then drain well and refrigerate while you make the dressing. Put the oil into a medium saucepan on a medium heat. Once hot, add the ginger, chillies, star anise and cinnamon and gently fry, stirring often to separate the aromatics, until the ginger is crisp and golden. This will take about 5 minutes but watch closely, as the ginger can turn from golden to burned quite quickly. Drain through a heatproof sieve set over a heatproof bowl to collect the aromatic oil. Set the crispy aromatics aside. Transfer 3 tablespoons of the aromatic oil to a separate bowl along with the soy sauce, maple syrup and sesame oil. Use any remaining oil for another recipe. Toss the noodles with the cucumber (avoiding the pickling liquid). Transfer to a lipped platter, then top with the tinned mackerel. Spoon over the dressing, followed by the crispy aromatics, spring onions and sesame seeds. Serve with lime wedges alongside.