Preheat the oven to 425°F (220°C). Line a large rimmed baking sheet with aluminum foil.
Make the chicken marinade by combining 2 tablespoons olive oil, 2 tablespoons soy sauce, 2 tablespoons lemon juice, lemon zest, 3 minced garlic cloves, and 2 teaspoons chopped thyme in a large resealable bag or bowl.
Add the 4 chicken breasts to the marinade, seal the bag (or cover the bowl), and refrigerate for 20–30 minutes.
While the chicken marinates, prepare the potatoes: in a large bowl toss 1.5 lb halved baby potatoes with 2 tablespoons olive oil, 3 minced garlic cloves, 1½ teaspoons smoked paprika, 1 teaspoon salt, and ¼ teaspoon black pepper until evenly coated.
Spread the seasoned potatoes in an even layer on one side of the prepared sheet pan, leaving space for the chicken.
Remove the chicken from the marinade and place the breasts on the empty side of the sheet pan. Discard the used marinade. Season the chicken lightly with salt and pepper, then top each breast with a lemon slice.
Bake for 15 minutes, then remove the sheet pan and toss the potatoes to promote even browning.
Return the pan to the oven and bake another 15–20 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the potatoes are tender.
Remove from the oven and serve the chicken and potatoes warm.
