How do you slip? How do you slip as you step fowards?

[AlexKid]

Basically I dont even know how to slip everyone does it differently and its frustrating because I dont know which one to learn.

Then how do you slip AS you come foward or cant you do that? Do you have to come foward and THEN slip?

(Basically im trying to step diagonally right and foward whilst slipping and throwing a straight left cross) (im a southpaw)