Madame Marissa has a gorgeous ass and she knows it. This guy tried to spank her thinking that she would be flattered and would take it as a flirting gesture. But she did not and she was offended by what he did. She was so pissed at him that she had to degrade him and she did this with her hiking boots. He was shocked and humiliated by it and he regretted what happened.
While madame Marissa made her slave lick her boots, she felt that it was not enough despite it being humiliating to him. She felt that she needed to do more to dominate as well as humiliate him and that is why she chose to turn him into a human ashtray. That was painful as it was humiliating and cumulatively, she felt that he had learned his lesson and she let him go.
Madame Marissa was out to boot torture this guy and she knew that she had to do it like a pro because she had to make sure that he learned his lesson from that one lesson. There was no going back and he had to do all that she said from then on. That is why she brought out her big guns and used the hiking boots to do it.
Madame Marissa felt that she had to test the slave's pain threshold because she wanted to teach him a lesson and do it in a way that he would never forget. The mistress knew how to go about it and that is why she used her hiking boots femdom to get what she wanted. And she loved the fact that she got what she wanted at the end of it all.