Lightly grease a large loaf tin (if it's not non-stick) and preheat the oven to 350 F (180°C).
In a small bowl, mix together the cornstarch, salt, cumin, coriander, paprika, turmeric, cloves, cayenne, and cinnamon.
Put the chicken thighs in a medium or large bowl and pour the oil over. Stir around to coat (I just use my hands), then add the dry spice mix and get the meat good and coated.
Layer the pieces of chicken in the loaf tin and press down, then bake for 40 minutes.
When the shawarma is ready, leave it in the tin for 10 minutes so that all the juices can go back into the chicken.
Tip it out of the tin and slice your shawarma. We like to eat this piled into flatbreads with the slaw. Any leftovers can be kept in the fridge, or frozen for the next time you need your shawarma fix.