One of the reasons this dish is so picnic friendly is because salmon tastes good hot, warm or cold. It doesn't matter. The cucumbers and radishes are pickled in dill and vinegar and are full of fresh flavours that all go well with salmon.
Peel cucumbers in lengthwise strips, leaving thin strips of skin between peelings. Either by hand or with a mandolin, slice cucumbers and radishes into very thin rounds. Place both in a bowl with rice wine vinegar, dill, sugar, and pinch of salt to season. Toss to combine, and set aside.
Season both sides of the salmon with salt and pepper. In a hot fry pan or on a hot grill, cook the salmon for several minutes, until nicely browned. Turn over, and continue grilling until just cooked through. Salmon will look flaky when done.
Place pickled cucumbers on a serving platter, top with salmon fillets, and serve.