Preheat the oven to 400°. Spread a 1/4-inch layer of kosher salt on a small rimmed baking sheet. Nestle the salmon in the salt, skin side down. Bake for 15 minutes, or until just cooked through. Using a spatula, lift the fillet from the skin and break it into bite-size pieces.
In a large bowl, whisk the oil with the vinegar, mustard and garlic; season with salt and pepper. Add the mesclun, tomatoes, olives, chives and basil and toss. Add the salmon; toss gently and serve.