Combine lentils, celery, shallot, thyme, and bay leaf in a saucepan. Add enough cold water to cover by 3 inches. Bring to a boil. Reduce heat, and simmer, stirring occasionally, until lentils are tender but not mushy, about 15 minutes. Drain, and discard bay leaf. Return lentils to pan. Stir in 3 tablespoons oil, 1 1/4 teaspoons salt, and pepper. Cover to keep warm.
Heat a skillet over medium heat. Lay 4 slices speck in skillet in a single layer. Cook, pressing flat with a spatula and flipping slices if necessary, until crisp on both sides, 5 to 6 minutes. Drain on paper towels in a warm place. Repeat with remaining 4 slices speck.
Return skillet with drippings to medium-high heat. Season scallops on all sides with salt and pepper. Add to skillet, and cook, flipping once, until both sides are golden brown and centers are opaque, about 2 1/2 minutes per side.
Add orange zest, lemon zest, parsley, and chives to the lentils, and stir to combine. Toss spinach with vinegar and remaining 2 teaspoons oil, and season with salt and pepper. Arrange scallops and lentils on 4 plates, and drizzle with oil. Top with speck. Place spinach next to lentils. Serve immediately.