As I've read it on this forum, the majority of hives that get started from packages and not treated, end up succumbing to mites.
Can't give you the full answer on what to do because nobody knows what that is. But here's a few pointers. Some bees have been bred towards mite tolerance, and some have not. If you don't want to treat you will need bees bred for that, not a breed susceptable to mites. So at some point after your package is in the hive and up and running, find somewhere to buy a queen that has been bred for mite resistance and requeen your hive with it.
Secondly, treatment residue in a hive is thought to aggravate mite infestation. Most comb foundation contains the residue of old treatments. So to avoid having old treatment residue in your hive right from the git go, you need to either source treatment free wax that has been made into comb foundation, or just block treatment free wax to paint onto plastic foundation, or don't use foundation and allow the bees to build their own comb without any foundation. To do that, you need to research "natural comb", to find out how to get the bees to build the comb where you want it, ie, in the frames.
Those two things, the bee breed, and a treatment residue free hive, to my mind would be the basic starting points for someone wanting to be treatment free.
Realise that no matter what you do, your hive may just get bigger and bigger mite numbers till it gets wiped out so a treatment free beekeeper must be prepared for the possibility of dissapointment. That, after all, is why most people treat, if they didn't have to, they wouldn't.
You may decide to use manipulations that are not supposed to be treatments, such as for example removing drone brood from the hive and destroying it. This helps because the mites are especially attracted to drone brood so you can get a lot of mites out of the hive by doing that, without using any chemicals.
Just get started, and keep reading. One thing I've found though, is what one person finds works for them, may not work for someone else. There is no way or nothing you can do, to guarantee you will be able to keep treatment free bees alive for the long haul.