Place your diced cucumber in a colander and sprinkle with the 1/2 teaspoon of salt, tossing a bit. Cover with a paper towel and a heavy bowl and let them drain for 30 minutes.
In a large bowl, beat the cream cheese with an electric mixer until fluffy. Add the lemon juice, garlic, dill, and a grind or two of black pepper. Beat until combined and then fold in drained cucumbers and taste for salt and pepper, adding any as needed. Chill for at least two hours so the flavours can combine.
When ready to serve, spread the cream cheese mixture on the crackers. Top with a hunk of smoked salmon and a wisp of dill.