While I absolutely agree with the above posts, I want to add a cautionary note. Not all models behave well in a slip. Many models will either pitch up (toward the canopy), or pitch down (toward the belly) in a slip or knife edge. This is just one more complication that a beginner must manage, and if he/she is trying out their first slip near the ground it could be that last "slip" that the model makes.

Practice this stuff at a safe height & be prepared for some bizarre behaviour.