The most important factor in the preparations of "sashimi" is the absolute freshness of the fish. Frozen fish cannot be used. It is best to avoid fresh water fish since they can carry parasites. Keep the fish refrigerated, wrapped in cheesecloth until ready to use. Handle the fish as little as possible; the warmth of your hands can spoil its freshness.
CUTTING the FISH: There are four basic fish cutting methods for sashimi and a very sharp, heavy knife is indispensable to them all.
1. Hira giri (flat cut): This is the most popular shape, suitable for any filleted fish. Holding the fish firmly, cut straight down in slices about 1/4 to 1/2 inch thick and 1 inch wide, depending on the size of the fillet.
2. Kaku giri (cubic cut): This style of cutting is more often used for tuna. Cut the tuna as above (flat cut), then cut the slices into 1/2 inch cubes.
3. Ito zukuri (thread shape): Although this technique may be used with any small fish, it is especially suitable for squid. cut the squid straight down into 1/4 inch slices, then cut lengthwise into 1/4 inch wide strips.
4. Usu zukuri (paper thin slices): Place a fillet of bass or porgy on a flat surface and holding the fish firmly with one hand, slice it on an angle into almost transparent sheets.