Your feet don't cross. The first foot steps, then the second steps or slides next to it in the same square - that's why it's listed 2 steps per block.
Now, for "fun"... you could try crossing legs, only hitting one foot per block. Either do it like step aerobics "grapevine" [step behind, little hip rotation] , or martial arts footwork - crossing over either in front or back, with a bit more hip rotation. You can find the grapevine on YouTube, but I didn't find a good version of the martial arts crossovers. It's basic white-belt karate stuff, so anyone who's had any karate should be able to show you.
Also for "fun" you could do 3M - tripedal motion. Do QM without one of your limbs. [like no right leg]. Pretend you're injured, and can't put weight on it.
These are just add-ons, or modifications to the official warm-up. You don't have to try them. Hope that helps!