Start with Ubuntu Mini Remixfor the base 

Use Customizer to add stuff

use usb-creator-gtk if making a live USB

the directory for the Live User will not exist, but you can create it and anything that you put there will be retained on the live boot

Execute Hook refers to a script to customize your CD if you are doing the same customization over and over again

The directory for the live CD is in /home/FileSystem in the host

To have something automatically run in foreground after boot add it to /etc/profile.d/bash_completion.sh

the iso is in the /home directory of the host

clean unmounts the iso

sudo has no password

/dev/ttyUSB0 and friends are not openable by default. You can sudo chmod 777 them in your script tho.

if you don't need the network and the boot is getting stuck waiting for it, comment out the sleeps in /etc/init/failsafe