Rinse chicken well inside and out. Pat dry.
Drizzle outside with a little olive oil and rub the olive oil all over the skin, top and bottom.
Sprinkle the whole chicken well with seasoning salt. Be sure to sprinkle the cavity well with seasoning salt, too. Rub the seasoning salt all over the skin, being sure to get some into any crevices.
Sprinkle with the smoked paprika all over the chicken, including the cavity. Again, rub this into the outside of the chicken.
Put a few pieces of the lemon and the onion, and half of the garlic in the chicken cavity. Fill the cavity, but do not stuff tightly.
Cross the chicken legs together and tie. Bend the wings backwards and tuck them under the chicken.
Place the aluminum foil balls in the bottom of the slow cook. Position them so that they will support the chicken and keep it above the cooking juices that will accumulate in the bottom of the slow cooker.
Place the remaining lemon and onion pieces and the remaining garlic in the bottom of the slow cooker.
Put the chicken on top of everything. Adjust the aluminum balls as necessary to best support the chicken.
Cook for about 3-4 hours on high until the juices run clear, or until the thickest part of the breast registers 165-degrees F on a meat thermometer.
Turn off slow cooker and allow chicken to rest for a few minutes. Remove and cut into serving pieces or allow to cool completely and remove meat from bones, then shred or cut into appropriate sized pieces.
If using the juices that have collected in the bottom of the slow cooker, remove the aluminum balls and strain the juice through a sieve. Press the aromatics that have collected in the sieve lightly to extract any remaining juice from them. The juices are great used in gravy, soup, or stock.