Spread clingfilm on a work surface and place one piece of salmon on it, skin-side down.
Spread the salt mixture (rest of the ingredients) on top and cover with the second piece of fish, skin-side up.
Wrap tightly, place on a baking sheet, cover with foil and top with another baking sheet.
Place tins on top to weigh it down and refrigerate for two days, turning every 12 hours.
To serve, gently rinse off the salt mixture with water, pat the salmon dry with paper towel and slice it wafer thin. Arrange on thin slices of rye bread and top with cucumber salad.