Time to get rid of the walls!
Again, try this in a low-distraction environment first. Your driveway is a good place to practice this (as you see in the video) – there might be a few distractions around, but it is not a completely novel environment and your dog should be familiar with it already.
If your dog is struggling – decrease the difficulty of the environment and/or the difficulty of the exercise.
You could for example first try some food engagement to awaken the dog’s enthusiasm and then switch to By My Side!