Many answers focus on taking something away, like taking away the freedom to lie or the freedom to not think about how our actions impact others. I kind of think all of these are, in some sense, "cheating" in the free will department. They effectively remove a choice we have in the current world (I'm assuming you're using the current human world as a baseline.)
The answers that are more about providing more options or things, I think, are closer to the mark, I'm just afraid that they might be mostly boring from a story/worldbuilding standpoint.
So, I am pretty sure that simply tweaking your world's natural environment in such a way that
- food is plentiful,
- predators are weak or uninterested in humans,
- the temperature and weather are always moderate enough that shelter is never a life-or-death concern or maybe even not that big of a comfort concern
would significantly reduce motivation to commit crimes like trespass, theft of food, etc. And all of these things also make the world more boring from a story standpoint, I think.
So, if we had all this in our current world, we might still fight about who gets to live on the beach or by the river or on the lake.
I wonder if you might get something interesting where one thing the god does is simply this: make it easy to leave a society and start over somewhere else. All of the above--shelter no big deal, gathering food and defense from predators trivial, etc, would contribute to this. But one thing that could really reduce conflict would be if you could just take the people that agree with you about how society should be and go do your own thing without a huge cost. In our world with finite arable/desirable land and difficulties in having reliable food sources and shelter and such, that's practically impossible to do.
But your world doesn't need to have that restriction. Maybe your world is the Mandelbrot set, and your people can just shrink down and find a very similar place to where they were just living but without the neighbors that were playing loud music at night.
A great deal of conflict could be avoided if it was easy to collect the likeminded and easily leave and resume your society without the un-likeminded. A fractal landscape is one possibility but portals to other equally livable planets or a planet that just kept growing and spawning new, equally fertile and equally temperate and equally surfable space; or any magical element that allowed trivial resettlement on uncontested land.
Stories are usually about conflict and this would reduce conflict. But maybe the conflicts that do come up, in the absence of our current conflicts, would be interesting. Think about social media--people find things to fight over, like reach and reputation and each other's attention and so on and it's essentially completely free form and resource-scarcity free. So maybe that's what becomes interesting; what do people yearn for and, eventually, fight over when basic necessities are abundant.