Slice yellow onion into fours and halve garlic head, then place on the bottom of the slow cooker. Remove any bags of gizzards, etc. from inside of the chicken.
Mix all dried spices in a small bowl and then sprinkle all around the chicken (top, bottom, and sides). Place chicken on top of onion and garlic and throw in any fresh spices. Drizzle a bit of olive oil on top of the chicken, then cover and cook on low for 6-8 hours. The vegetables and chicken will create its own juice, but feel free to add a tiny bit of stock if you like.