slow cooker soup recipe

[MadauntofA]

I have been busy today - cooked a roast chicken and made some stock! I would love to come home from work tomorrow to a chicken and veg soup so...
Do I sweat the onions/ celery before going in the slow cooker?
Do i put everything in including the cooked chicken pieces and chopped kale at the start?
Is 8hrs too long or will it be ok if left?
Thanks