Preheat the oven to 200°C (180°C fan) or Gas Mark 6 and line a baking tray with baking paper or foil for easy cleanup.
Pat the boneless, skinless chicken thighs dry with kitchen paper to help the seasoning stick and encourage a slightly crispy exterior.
In a small bowl, whisk together the salt, black pepper, garlic powder, onion powder, smoked paprika and dried thyme.
Drizzle the olive oil over the chicken thighs, then sprinkle the seasoning mix over both sides and rub to coat each piece evenly.
Arrange the thighs in a single layer on the prepared tray, making sure they aren't crowded, and bake for 20-25 minutes.
Check they're cooked through by inserting a meat thermometer into the thickest part – it should read 75°C.
Remove the chicken from the oven and let it rest on the tray for 5 minutes before slicing or serving.