Preheat the oven to 425°F (220°C).
Slice half the lemon into thin rounds and set aside; cut and reserve the remaining half for squeezing over the chicken later.
Pat the chicken thighs dry with paper towels. Season both sides with salt, black pepper, and about 1/4 teaspoon ground thyme total.
Heat 1 tablespoon olive oil in an oven-safe skillet over medium-high heat until shimmering.
Place the thighs skin-side down in the hot skillet, pressing gently so the skin makes full contact; cook until the skin is well browned and crispy, about 4–6 minutes.
Flip the thighs, nestle the lemon slices between the pieces in the pan, and squeeze the reserved lemon half over the chicken.
Transfer the skillet to the preheated oven and bake until an instant-read thermometer inserted into the thickest part of a thigh reads 165°F (74°C), about 15–20 minutes (longer for very large thighs).
Remove the skillet from the oven and let the chicken rest for 5 minutes before serving.