We do not necessarily want to make major modifications to our game's terrain. We previously spent considerable time planning, creating, and fine-tuning the terrain. Instead, we will select one of the large, flat areas to act as a sandbox. If you do not have any large, flat areas, you can select one of your flat areas and make it a bit bigger.

The following image suggests a size relative to our current game world. The white box towards the bottom center of the image represents an ideal size:

Now that we know where our sandbox will be, let's prepare the Hierarchy panel for any new items we create for the sandbox. Simply right-click in an empty area of the Hierarchy panel and select Create Empty. With that new GameObject selected, rename it in the Inspector panel as Sandbox.