Wash whole chicken thoroughly, remove any inside parts (neck, etc.)
Place chicken in a slow cooker.
Dice peaches in thick slices. Slice onion in the same way – into 8-10 large slices.
Sprinkle diced peaches and sliced onions on top of the chicken and around the sides of it in a slow cooker.
Pour white wine along the sides of the slow cooker, so that white wine just goes straight to the bottom.
Generously sprinkle salt and pepper on top of the chicken and on top sides of sliced peaches, onions slices.
Sprinkle capers on top of the chicken and sliced peaches.
Close with the lid and set on “LOW” setting to cook for 7 hours. Or, set it to “HIGH” setting to cook for 3 hours. As the chicken is cooking, check your slow cooker occasionally. Depending on the size of your slow cooker, the chicken coupled with wine might produce too much liquid, in which case you occasionally pour that liquid away into a separate bowl and save it for later (to serve with chicken or use with other dishes as an "enhanced" chicken stock).
When serving, garnish with sliced fresh peach (optional)