Start with the Earth as a template. Wind back the environmental damage that has been done by humankind over the centuries and restore the multitude of species that have been wiped out.
Move those people who won't live in harmony with the restored environment to a duplicate Earth that has the same ammenities the restored Earth now has. If they end up destroying it again, that is their problem.
On the restored Earth, train people on how to get along with the environment and each other. You can start with the Golden Rule, but applied to both the enviroment and people. Seek harmony in all things.
But also allow for change. I would love to see this dream Earth be technologically advanced, even though you may not think it is because it lacks huge factories and giant mines. If things are designed with the entire life cycle in mind, including generating the materials that go into them, pollution could be minimal. Heck, the byproducts from one set of processes could be the raw material for another.
Over time, in this dream world, I could see other species, like dolphins, whales, the great apes, dogs, cats, and horses becoming an active part of said world, intelligently interacting with humans and the environment. They would almost be sybling races.
And to allow for things like meteor strikes and the death of the sun, we would have space travel.
