Select the remainder of the shelled out face.
Select “DRAW”. This icon is highlighted in the photo above.
Draw the outline of the side you wish to create. (this must be a closed figure and will be indicated as such by the brown color seen above.)
Select “SOLID”. This icon is highlighted in the photo above.
Select the shape you drew in step eight. An icon will appear as seen in the above photo.
Select “EXTRUDE”. This icon will appear by rolling the mouse over the previously mentioned icon.
Input the negative value of the wall thickness of the rest of the part. (this will default the computer to changing it to a cut extrude but will be fixed in the next step.)
Select the drop down box highlighted in the above photo. (for those who care this is called the “Boolean” options.)
Select “JOIN”. This will change the extrusion back to a normal bass/boss extrusion.
Select “OK”. This icon is highlighted in the above photo.