Slice your potato in to 1/8-1/4 inch thick slices, leghthwise.
Heat 1 tbsp cooking fat in a large skillet on medium high.
Add in potato slices evenly distributed, sprinkle lightly with salt.
Cook 5 minutes each side and then cover for a 2 minutes at the end.
Transfer to a board. Season fish with salt and dill.
Heat second tbsp of cooking fat in the same skillet.
Sear the 4oz fillet, 2 minutes each side, then cover for 1-2 minutes. Done.
Slice the avocado.
Build your toasts, alternating toppings in different combinations: mayo and mahi, avo and mahi, avo and lemon with herbs, pate with fish etc.