Trim the stalks from the fennel, reserving the lacy tips of the fronds for garnish. Slice the fennel bulb lengthwise into ¼-inch-thick slices. They will look like hands. Slice these lengthwise into ½-inch thick slices. Set aside.

Cut the lemons in half, then cut each half into 3 pieces. Discard the seeds. You should have about 1½ cups of lemon cubes. Put the lemons in a bowl and sprinkle them with the salt. Add the chicken, oregano, pepper and garlic and turn together. Let stand about 30 minutes.

In a heavy-bottomed saucepan or Dutch oven, heat half of the olive oil over medium-high heat. When it is hot, add the chicken thighs and lightly brown them, turning several times, about 10 minutes.

Remove the chicken and add the remaining olive oil and the fennel. Reduce the heat to medium and saute the fennel, stirring, until it is nearly translucent, 8 to 10 minutes. Stir in the lemons, turning a few times, then add the white wine and water. Scrape up any bits clinging to the pan, then return the chicken to the pan. Cover, reduce the heat to low, and cook until the chicken is tender and the fennel can be cut with a spoon, about 45 minutes.

While the chicken is cooking, mince enough of the fennel fronds to make 2 tablespoons.

Combine this with the lemon zest and set aside.

To serve, remove to a serving bowl or platter and garnish with the fennel fronds and lemon zest and, if desired, the optional green olives.