when working on the HandsOn3 you will see that the notes for the tutorial are hosted at SLAC with rather "generic" instructions. I have translated them into 'iridium-able' commands ;-)

===================================================================================
BLOCK 1  OPTION: SEPARATE build and source directory - getting the exercise code and compile
===================================================================================

$ mkdir ~/HandsOn3          # make new working directory
$ cd    ~/HandsOn3          # change to your new working directory
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn3/HandsOn3.tar.gz
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn3/HandsOn3-solution.tar.gz
$ tar xzf HandsOn3.tar.gz   # extract source code
# optionally extract in a similar way the solution. But please give the exercise a try first ;-)
$ mkdir build-HandsOn3
$ cd build-HandsOn3
$ cmake ../HandsOn3
$ make
$ ./SLACtut

# If at the time of quitting the execution you do not return to the prompt, you can try
# to 'kill' the process by pressing 'C-c' (Control key + c key)

===================================================================================
RINSE AND REPEAT
===================================================================================

# ... modify files located under '~/HandsOn3/HandsOn3'
# compile the code at ~/HandsOn3/build-HandsOn3
$ make
# when you issued 'cmake ../HandsOn3' those two folders got linked. It would just work

# If at the time of quitting the execution you do not return to the prompt, you can try
# to 'kill' the process by pressing 'C-c' (Control key + c key)

===================================================================================

OR

===================================================================================
BLOCK 1  OPTION: SAME build and source directory - getting the exercise code and compile
===================================================================================

$ mkdir ~/HandsOn3          # make new working directory
$ cd    ~/HandsOn3          # change to your new working directory
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn3/HandsOn3.tar.gz
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn3/HandsOn3-solution.tar.gz
$ tar xzf HandsOn3.tar.gz   # extract source code
# optionally extract in a similar way the solution. But please give the exercise a try first ;-)
$ cd HandsOn3
$ cmake .
$ make -f Makefile
$ ./SLACtut

# If at the time of quitting the execution you do not return to the prompt, you can try
# to 'kill' the process by pressung 'C-c' (Control key + c key)

===================================================================================
RINSE AND REPEAT
===================================================================================

# ... modify files located under '~/HandsOn3/HandsOn3'
# compile the code directly at ~/HandsOn3/HandsOn3
$ make -f Makefile

# If at the time of quitting the execution you do not return to the prompt, you can try
# to 'kill' the process by pressung 'C-c' (Control key + c key)

==================================================================================