First let's open up Blender, Press A and then A again to select everything and delete all the default items.
*Hint: First Extrude all 4 sides inwards, and then extrude the middle of the sphere (Kind of like a belt) *
There is a good Blender lesson on UV Mapping if you are new to UV Mapping in Blender:
Select the entire object, press U and click Smart Unwrap project. Then open the UV Editor view in another window.
Note: Don't worry about the color changes in the future. You can change that in Unity later on.
Download Here (Or you can create your own):Download Tina's_Cubes_Package.unitypackage