In a medium bowl, combine potato slices, carrots, onion slices, 1/8 teaspoon salt, and pour the garlic oil mixture into the bowl and stir together to coat the vegetables..
1 yukon gold potato, ½ carrot, 1 slices red onion
With a paper towel, pat chicken breast dry, season both sides with salt and pepper.
1 (6-ounce) chicken breasts, salt and pepper to season
Arrange potato slices in two rows in the center of the sheet of foil. Place the chicken breast on top of potatoes and surround with carrots and onions. Drizzle any leftover oil mixture over chicken.
Fold foil packet tightly, sealing edges but leaving room inside. Chill packet for at least 1 hour (up to 24 hours).
Preheat oven to 375°F, placing rack in the lowest position. Put foil packet on a rimmed baking sheet and bake until chicken reaches minimum 165°F (about 30-35 minutes). Use a thermometer to check temperature.
Let packet rest for 3 minutes, then carefully open (watch for steam). Transfer contents to plates, drizzle with lemon juice, sprinkle with chives, and serve.