Crush the juniper berries, coriander, and the peppercorns in a mortar. Transfer to a bowl and mix with the sugar, fennel, and salt. Spread 1-2 tablespoons of the spice mixture into a flat shape.
Rinse the salmon, pat dry, and place the salmon skin side down onto the spice mixture. Coat the rest of the salmon with the remaining spice mixture. Wrap the salmon with plastic wrap, and seal well. Let infuse in the refrigerator for 24-36 hours.
Rinse and dry the dill. Remove the leaves and finely chop. Remove the salmon from the spice mixture, rinse well, and pat dry. Thinly slice, and arrange the slices on chilled plates. Sprinkle with the dill and serve.