Combine all of the spices in a small bowl.
Chop the onion into big chunks and place them in the bottom of your slow cooker.
Remove any giblets from the inside of the chicken (many are already removed by the butcher). Rub the spice mixture all over the chicken, including under the skin, inside the cavity, and any cracks/crevices.
Place the chicken in the crock pot on top of the onions. No liquid necessary, I promise! Cover and cook on high for 4 hours or low for 6-8 hours, until the chicken is (literally) falling off the bone.