Begin by placing each boneless chicken thigh between two pieces of plastic wrap. Using a meat mallet, pound the chicken to achieve an even thickness of about ½ inch.

In a mortar and pestle, combine paprika, coriander seeds, black peppercorns, dried rosemary, red chili flakes, and coarse sea salt. Grind the spices until fine, then mix in the finely chopped garlic, olive oil, and freshly squeezed lemon juice until well blended.

Thoroughly coat the chicken thighs with the prepared marinade, ensuring every piece is well covered. Refrigerate for at least 2 hours, focusing on overnight for optimal flavor.

Take half an onion and insert a bamboo skewer into its center to create a stable base for cooking.

Stack the marinated chicken thighs onto the bamboo skewer vertically.

Preheat your oven to 375°F (190°C) and place the skewer upright in a baking dish. Bake for 1 hour, or until the internal temperature reaches 165°F (75°C).

Allow the chicken gyros to cool for approximately 15 minutes before carefully shaving off the cooked meat to serve.