This guy was helping me with my model online with this tutorial, but at the mesh under the cube he insets a face, how did he do it? Thanks.
You can do this using the 'Inset' tool.
Select the faces you want to inset:
Press I to trigger the 'Inset' tool and move the mouse to increase or decrease the amount. Press B during the inset to turn on the 'Boundary' option (which will stop creating faces along the boundary of the mesh):
Press Enter when you are happy with the inset and then delete the inset faces with X> Faces