The King makes Gulliver kneel in front of him and lick the ground in front of his feet. This is a common practice in this kingdom, and Gulliver does it willingly (in part because the man has no pride). The ground can be very gritty because the King doesn't always order it cleaned. Sometimes, after greeting the King this way, his subjects stand before him with their mouths full of dust, desperately trying not to cough. This is because coughing in front of the King is against the law and could get them executed.
We also learn that sometimes, the King assassinates people he's not fond of by sprinkling the ground in front of his feet with poison. So, when they greet the King, his subjects never know if they're going to live or die from the experience. What's more, accidents have happened in the past where the poison hasn't been properly cleaned up and people have died. The King has been sorry about this, but not sorry enough to stop his weird, dangerous method of execution.
You can still add more to this. Hope it helps :)
