Start the preparing the dish a few hours before cooking the rice. Take a dish lager then mackerel and covet with the thick layer of salt, then place the mackerel on it and cover completely with the thick layer and keep it 3to 4 hours. Remove the mackerel and rub off the salt with damp paper towels. Carefully remove all the bones and tweezers. Then put in a dish and pour the rice vinegar on it leave for 30 minutes. Slice the Pieces into Half inches pieces.
Make the Vinegared Recipe ( See the Recipe),
Mix the hand vinegar ingredients and keep aside.
Using finger carefully remove the transparent skin for each mackerel fillet, starting at tail end, Put the fillet and skin side down, on a cutting board and slice off the highest part. So the fillet can be flat. Keep the trimming aside in a bowl.
Line a rectangular container or wooden mould with a large piece of with a large piece of plastic wrap.
Put a fillet, skin side down, in the mould or container; fill the gap with the other fillet or trimmings. Dip the finger hand in the hand vinegar, then press the cooked rice firmly on the top of the fish, Put the wet wooden lid on the top, or it can be folded in a plastic by putting weight on top.
It can be left on room temperature for a few hours. At the time of serving take out from container and unwrap the plastic.
Use a very sharp knife and wipe it with vinegar-soaked paper towel. Cut the sushi into cubes by cutting both side and serve it with a little soy sauce and pickled ginger.