Place the baguette slices on a baking sheet. Brush them with olive oil, and lightly sprinkle them with salt. Bake for about 4 minutes, until golden around the edges, but not hard—they will firm up as they cool. Let them cool to room temperature.
Dollop/spread some Herby Mayonnaise on each of the crostini. Drape a piece of smoked salmon on top, give it a light grind of pepper, then sprinkle over a tiny bit of lemon zest, if using, and place a little bit of the fresh herb of your choice on each.