What is the best way to keep a weed free garden?

You can put down a weed mat, and over it with bark.

Landscape fabric covered by mulch. Or consider using a preemergent like Preen, just read the label carefully, can be dangerous to pets and children if used incorrectly. Or you can weed every day 15 minutes or so at a time. That's what I do, when I go out to exercise the pets, I spend a goid 15 minutes or so digging stuff up. Or if budget allows, hire a service to come do it for you once a week or on an as needed basis. Having a garden is work, I enjoy it, so for me not a dreaded chore.

Lay down some landscape fabric and two to three inches of mulch on top. Cut openings for plants or around existing plants.

Use mulch to help prevent weeds around flowers: https://www.craftylittlegnome.com/use-mulch-garden/