Reply To: On Mesh Modeling Exercise 1, I have loop cut the cube to make the 90 degree cutouts on the corners. However, when I make …

You are not required to follow the examples. Best way to do the corner insets of the cube is to select all the faces and use the inset tool with the cntrl key constraint.

Here is a thread showing one way to do the corners.
http://community.cgcookie.com/t/help-needed-on-the-mesh-fundamental-exercise/2370