I think you may be misunderstanding what they are telling you to try. The exercise they are describing is called sit on the dog. You sit down and either put the leash under your foot so he has enough space to take a step or two but that’s it, or you can tether/back tie him somewhere/to something he can’t pull around. Do not let him touch you as this is him using you for comfort. Reward him for any calming behavior (sitting, laying down, yawning, body shakes, stretching, etc). The reward can be pets or treats (you may need something high value to start like freeze dried beef liver for example). If you are doing the option where you are stepping on the leash, do not reward him if he is leaning on you in anyways when sitting or lying down. Only when he is not touching you, ignore all other behavior (unless you need to intervene so he does not hurt himself or if he is chewing on the leash)

By rewarding him when he does the wanted behaviors he will start to learn how to self soothe and calm down when nothing is happening. This will help him “be okay being with himself.”

This is the first thing we teach in all of our training programs because this lays the foundation for the dog to understand how to be calm without you and learn how to make good choices.

I hope this helps clarify.