Combine all of the spices in a small bowl and set aside.
Place the onion in the bottom of your slow cooker.
Remove any giblets from the chicken (or leave them if you wish, but be sure to remove any plastic or paper bags, then rub the spice mixture all over the outside of the chicken. You can even put some of the spices in side the cavity and under the skin covering the breasts.
Put the chicken breast-side-down on top of the onions and cover the slow-cooker (note that my photos show breast side up- it turned out perfectly delicious that way too). There's no need to add any liquid.
Cook on high for about 4 hours or on low for 7 hours, or until the chicken is falling off the bone. Remove the edible chicken pieces from the slow cooker and serve.