The first Basic Game Objects I made was a Crate to do this I made a 0.5m Box and then I add a modifier to it called Edit Poly to help me shape the Box the way I want it so it looks like a Crate. In the Edit Poly I used Polygon then got all the sides and used Extrude two but on the second one I made it go in by doing -0.05m.
Game Design 