Find a suitable low deck. (The one pictured is a fraction too low and would be more suitable 1 m off the ground).
Hoppers check with your parents first. You may want to add some bits of wood just on the inside of the boundary joist to give you something to grip. Any wood you use wants to be pre-drilled before you screw it, to reduce splitting the timber. You can then shimmy along the deck in both directions practicing your toe hooks and heal hooks.