The "Other Side" as you put it, is still there, and still supplies "Zero Point" energy to this universe (and all other universes attached to it).
Other "Manifolds" could exist beyond our multiverse's one as well, ie multi-multiverses, all the way up.
These would be distributed normally, and infinitely, but hard for a human to gain access to. (ie. wormholes to parallel universes/time-travel).
If you want to imagine what it looked like, when this universe began, try imagining a 10 dimensional lightening bolt, with each fork ending in a
single point particle (you'd need a fork for each fundamental particle in existence, at all points in time).