Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Place the cooked lentils on a clean kitchen towel or paper towels and pat them thoroughly dry to ensure they crisp up in the oven.
In a medium bowl, toss the dried lentils with 0.5 tablespoon of olive oil, dried oregano, half of the sea salt, and half of the black pepper.
Spread the seasoned lentils in a single layer on one side of the prepared baking sheet.
Brush the chicken breast with the remaining 0.5 tablespoon of olive oil and season both sides with the remaining salt and pepper, then place it on the other side of the baking sheet.
Roast for 20 to 25 minutes, stirring the lentils halfway through, until the chicken reaches an internal temperature of 165°F and the lentils are crunchy.
While the tray is roasting, finely mince the garlic and chop the fresh parsley.
Remove the tray from the oven and immediately transfer the hot lentils to a bowl; toss them with the lemon juice, lemon zest, minced garlic, and fresh parsley.
Slice the roasted chicken breast into strips and serve it alongside the warm, fragrant lemon herb lentils.