Kind of just an idea thing that can possibly be adopted by canon.
The Void is a dimension that holds all other dimensions in existence. It's edges are portals that transport to the opposite of itself, and there is no space beyond it. It holds the dimensions of THE PRISM (The main FB universe), THE SPHERE (The Bizarro Universe), THE PYRAMID (Doublizarro universe), THE SEPAR, the GENESIS POND (The universe in which all S---B Sessions take place), EVERSPRING, the GREY ZONE, and some other dimensional planes. It is considered a 'Multiverse' of sorts and the dimensions it holds are figured as shapes of sorts that, when touched, will transport the thing or person that touched it into that dimension with a relative size, as when inside The Void, each dimension will appear to a relative size of six feet in diameter or height. Method of entering The Void is unknown, though it is known that there are an amount of methods that can connect the dimensions in The Void (Most notably, connections between The Prism and The Separ or The Prism and The Sphere.). It is known that Genesis Frogs will appear in The Void as a geometrically-shaped dimension. Dimensions are usually surrounded by smaller objects which are representative of alternate timelines that are not considered to be the Alpha Timeline.
The Void was originally the plane of existence that was inhabited by Chaos, and then Gaia, before dimensions were created. The Separ would work as a dimension through which all concept could exist in other dimensions, which is why the gods inhabited that realm.
Work in progress.