Place the salmon into a large roasting tin or a fish kettle and cover with water. Squeeze in the lemon juice and add the rinds to the tin, then add the peppercorns and bay leaves.
Bring to the boil, then remove from the heat immediately. Set aside for the salmon to slowly poach in the residual heat for about 30 minutes, or until cooked through (the flesh should be opaque all the way through).
Using a fish slice, carefully remove the salmon from the tin and place onto a large serving platter. Remove the skin from the presentation side, from behind the gills to the tail.
Thinly slice the cucumbers, then halve each slice into little semi-circles. Layer the cucumber slices over the exposed salmon flesh in a pattern to mimic fish scales.
Surround the salmon with salad leaves.
To serve, pipe the mayonnaise over and around the salmon as desired.