if i am fighting as as a southpaw against a right opponent, which way do i slip to avoid his right cross? im assuming i would slip to my right (his left) , away from his right, is this correct?
Yes correct.
You should keep your lead foot on the outside of
his lead foot. That will keep you almost out of
reach from his right cross and his head will be right in your line of fire.
I'd be careful slipping the right cross to your right as a southpaw. That's a good way to run into a left hook.
Straydog has good advice about foot placement. I recommend slipping outside the right cross while parrying or taking a small step backwards and countering with a right hook as the cross comes in.