Tales of Tolgard
A pocket dimension is a finite dimension generally grown or created for some specific purpose. Desired for their privacy and security, the actual creation of a pocket dimension is quite difficult. Pocket dimensions are lesser forms of demi-planes envisioned by mortal minds and created through mortal powers whether divine, psionic, or arcane.
When a pocket dimension is created, all of its features are planned out ahead of time. For example, if one desires, it can be perfectly flat or extremely mountainous. A rough outline of how the world will be when grown dictates the landscape as the dimension grows.
Pocket dimensions are not actual planes per se but are rather a small stretch of reality that can only be reached from the Material Plane by either a magical gate, a talisman, or a spell cast by the pocket dimension’s creator.