I've locked the slave's face in the face trampling box and then start to walk all over his face with my dirty hiking boots! The deep, sharp-edged tread leaves behind nice imprints on his skin and hurts him a lot - but this is not the only way, he's going to suffer today. He also has to stick out his tongue, so I can wipe my dirty boot soles all over it. His tongue has to collect all the dirt that's stuck in the deep tread - and of course, he also has to swallow all of it! Then his face is trampled again under my full weight - covering his face with boot imprints for everyone to see!