Nature of the Dream Realm
The Realm of Dreams seems to be a corridor with many indistinct doors, leading to different peoples' dreams, apparently not limited to Orchid Bay citizens as when Juniper chases Steven through different peoples' dreams, you can also see a man stranded on an island, which seems to be something further from a dream as Steven is left stranded here as well. This suggests the realm is comprised of everyone's dreams. However, when Steven constructs his stairway building to the portal that could take him to the waking world, he only uses sleepers from Orchid Bay to achieve this.
In season 2's Dream Date, Steven is stuck working in a burger joint and wants to get back into the realm. Monroe shows Steven that it is actually relatively easy to return to it, as there are many different portals opening to it, the only real trouble being knowing the different times for the portals.