Every king needs a throne

Inspired by a prompt by HalfBloodPrincess69 on discord.
Prompt: Tom always treats Harry like royalty. So much, that he is deemed "King Harry" by Tom. Harry decides that every king needs a throne. Harry wants his throne to be Tom's lap.

Or in which Tom's little joke becomes a reality, and Harry is a sneaky Slytherin. Also, Draco should get new friends.