Newbie sort of thing

I ran into this

I'm very sorry forum members, but due to technical problems, I just cannot try it out. But anyway, is there a way, to create (easy and a hard way) your own, customized ubuntu .iso? (I'm sure that is)

What I mean is: after I boot my Ubuntu Live Cd, I will install ubuntu-restricted-extras, I will also add some plugins to firefox, but then, I want to uninstall programs like Libre Math or games I will never play. Then I want to burn it and make LiveCD out of my version of Ubuntu. And here comes the question: how to?

I tried some web searched about this, but the conditions are not, well, favorable at the moment...

I have never tried this app from above, but as I am always eager to learn, what's the hard way to do this?