There is a very simple way to create an OS X 10.11 El Capitan installer.
You need the full installer of OS X 10.11 El Capitan and a USB Drive (or something similar)
OS X 10.11 El Capitan has an executable file createinstallmedia to make a bootable usb.

Command to make an external OS X 10.11 El Capitan installer
This is assumes you have a an external partition named "YOURVOLUMENAMEHERE” (You should probably change your volume name)
Make changed where appropriate

sudo /Applications/Install\ OS\ X\ El\ --volume /Volumes/YOURVOLUMENAMEHERE/ --applicationpath /Applications/Install\ OS\ X\ El\ --nointeraction

2. Type in your password (Assuming you are an admin)
3. You will see the following:

Erasing Disk: 0%... 10%... 20%...100%...
Copying installer files to disk...
Copy complete.
Making disk bootable...
Copying boot files...
Copy complete.