Use the apostrophe, e.g. "Floridarolf's incorrect way of spelling, 'genitive' substitutes an 'e' for the latter 'i'."
Ok, I spelled "genitive" wrong. A look in the dictionary would have helped me. What I was asking about was where to set the commata.
In school we were told that "It doesn't matter too much. You won't get tested on that" (and I've made my Abitur).