If your world have "chantless/worldless chant" spellcasting magic; how does it work?

this has been spinning in my head some time...

And it really bugs me that (even if its plausable) normally, spellcasting without chants it's just as it says "you have idea in your head, you don't need a word to project the image in your head; shoot big ass fire ball".

Ok, as i said, is plausible that if you have trained enough some things will come out naturally, but if you make that some kind of method, what's the methodology behind it?