First step is to teach the dog to back up. It increases rear end awareness.
Try to keep your hand with food level with the nose. If you hold your hand with food too high, the dog will sit. If you hold your hand too low, the dog will lie down.
At this time, all we need are a few steps backwards.

If the dog is struggling with keeping her rear up, a second person can hold a leash tied around the dog’s waist. The Assistant cannot move until the handler gives the dog the signal to move back, otherwise the dog will become dependent on the help of the second leash.