Combine all the ingredients for the West Indies 5-spice and set aside. The recipe makes more than you will need for this recipe. Remove 1 tablespoon of the 5-spice for marinating the fish.
Cut the mahi-mahi into roughly ½” cubes, slightly smaller than bite-size. Put the fish in a bowl or zip-top plastic bag. Add the ¼ cup of West Indies 5-spice, salt, and 2 tablespoon of the olive oil. Coat the fish with the seasoning completely. Cover and put the fish in the fridge for at least 20 minutes and up to an hour.
Prepare the Salsa
Combine all ingredients in a bowl and mix thoroughly. Place the salsa in the fridge for at least 30 minutes and up to an hour.
Cook the Fish
Heat a large nonstick skillet on medium heat with the remaining 2 tablespoon of olive oil. Dust the fish with the flour, without letting it clump. You just want a thin layer of flour. We use a zip top bag or a large bowl to accomplish this. Add the fish and cook, until they are done, turning gently with tongs as needed to brown all sides. This should only take about 6-7 minutes in total (test a piece for doneness after 5 minutes).
Heat the tortillas, either in an oven or directly over a gas burner. Serve the fish tacos with salsa on top and some hot sauce if desired.