Please read about Deep-Frying.
Combine in a medium bowl:
Spread in separate shallow bowls:
Whisk together in a third shallow bowl:
Form the balls from ¼-cup scoops of the salmon mixture. Gently roll each ball in the flour until coated, dip in the beaten egg, then roll in the bread crumbs until coated. Set aside on a plate to dry for 10 minutes.
Heat to 375°F in a deep-fryer, deep heavy pot, or Dutch oven:
Gently drop 4 croquettes at a time into the hot fat and fry until deeply browned on all sides, about 2 minutes. Remove with a slotted spoon and drain on paper towels.