Marinate fish. In a medium bowl, whisk together olive oil, lime zest, fresh lime juice, ground cumin, smoked paprika, garlic powder, kosher salt, and black pepper. Pat the fillets dry, cut them into 2-inch cubes, and add to the marinade, spooning it over the top until the fish pieces are well coated. Marinate for 10-15 minutes.
Warm tortillas. Warm in a dry pan, directly over a low gas flame, or in the microwave according to package instructions until lightly golden brown and pliable. Cover with a tea towel until ready to use.
Make slaw. In a large bowl, toss cabbage with cilantro, lime juice, salt, and a drizzle of olive oil.
Dredge. Add the potato starch to a shallow bowl. Dip the marinated pieces of fish in the potato starch until thoroughly coated. Transfer to a plate.
Cook fish. Heat a large skillet with enough avocado oil to cover the bottom over medium heat. Arrange the cod in a single layer and cook for 3-4 minutes on each side until golden brown and crispy or until the internal temperature has reached your desired temperature.
Assemble. Load up tortillas with chili lime mayo, crispy fish, and slaw. Serve with lime wedges.