Looking for that mix of crown jewels and, well, other kinds of jewels? The 'slut princess' niche is pretty specific but once you know where to dig, it's a treasure trove. A lot of these are tucked away in the Kindle Unlimited vaults, often from authors who specialize in royal fantasy romance with a heavy dose of spice.
For pure steamy adventure, Sierra Vane's 'Her Royal Plaything' comes to mind. It's less about political intrigue and more about a princess on a diplomatic mission who gets... distracted by the rugged captain of the royal guard during a perilous journey through a monster-infested forest. The 'adventure' is basically an excuse for constant tension and survival-hookup scenarios.
If you want more plot with your spice, Lexi C. Foss has a series starting with 'The Princess and the Beast'. It's a loose fantasy retelling where the 'adventure' is the princess being offered to a monstrous lord to save her kingdom. The journey to his castle and the subsequent unraveling of the curse are packed with dark, steamy scenes against a backdrop of real danger.
Honestly, a good chunk of these stories use the 'quest' or 'escape' narrative as the perfect engine for forced proximity and high-stakes encounters. You just have to accept that the world-building often takes a backseat to the chemistry.