Rinse the zucchini but do not trim them. Bring a large saucepan or stockpot to a steady boil. Add the zucchini, but don’t cram them together or boil them too vigorously, because you want them to remain whole.

Cook for about 20 minutes, partially covered. Near the end of the cooking time, check for doneness by lifting one squash from the water with a large slotted spoon or spatula. A perfectly cooked zucchini will be just soft enough to droop a bit on the spoon but won’t break apart.

Carefully remove the zucchini, one at a time, to a colander or wire rack and lay them flat. Sprinkle about 1/2 teaspoon of the salt over the squash, rolling them to distribute the salt evenly. Let cool for a few minutes.

When you can handle them comfortably, trim the ends from each zucchini and cut them in half crosswise, into 3-inch pieces. Slice all of these lengthwise in half, and again into quarters, to form wedges. Arrange the wedges neatly on a serving platter, cut side up, in one or two layers, so you can dress them easily.

Sprinkle another 1/2 teaspoon of salt evenly over all the slices (you may need a bit more if using very coarse grains of fleur de sel). Then drizzle all over the three tablespoons of oil and scatter the lemon zest. Let the zucchini absorb the flavors for a while before the final seasoning.

Just before serving, sprinkle the lemon juice over the wedges. Taste a piece and add more salt or lemon juice if you like.