Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Prepare the vegetables by trimming the ends off the Brussels sprouts and slicing them in half, then peeling the carrots and cutting them into 1-inch rounds.
In a shallow bowl, whisk together the almond flour, garlic powder, dried thyme, lemon zest, 0.25 tsp of sea salt, and 0.125 tsp of black pepper.
Pat the chicken breast completely dry with a paper towel and brush it with 1 teaspoon of the olive oil.
Press the chicken breast firmly into the almond flour mixture on both sides until evenly coated with the herb crust.
In a medium bowl, toss the prepared Brussels sprouts and carrots with the remaining 2 teaspoons of olive oil and the remaining salt and pepper.
Arrange the crusted chicken and the vegetables in a single layer on the prepared baking sheet, ensuring they are not overcrowded.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with golden, caramelized edges.
Allow the chicken to rest for 5 minutes before slicing to keep it juicy.