The simplest possible universe is the one in which God is real, and everything else is within the mind and/or imagination of God. This is as envisioned by British philosopher Bishop Berkeley. The technical name for this is Ideal Monism, and it has been very much out of fashion as an idea for a long time. However, there are advantages to it. It is actual quite easy to derive a physical universe this way, once we understand that physics is just rule-following behavior. Just as a role-playing game player simulates a physical universe in a game such as Dungeons & Dragons with the aid of a set of dice, a entity of infinite intellect could quite easily generate a “physical” universe from the subatomic level up, by imagining all the individual trajectories of subatomic particles, and then contemplating the result (which would then generate the experience of the universe we call consciousness).
This is a main topic in my forthcoming book, “The Human Future,” so please watch for it when it comes out.
xkcd 505: A Bunch of Rocks by Randall Munroe