Usually, in order to do something, we need to be well-prepared for it. For example, if you want to cook a dinner, you have to go to the market, choose fresh food, bring it home, season it. After that, you are now ready to cook. So, if you have someone else done all that stuff for you, then your only job now is just cooking. Is there an idiom or set phrase for this? I think just saying "just cook" is so simple.
My initial intention is to use it for cooking only, but general idioms are welcomed.