You can try Archive of Our Own (AO3). It has a vast collection of fanfiction from various fandoms, including many for the Arthurian legend. Just search for the relevant tags like 'Arthur spanks Merlin' and you might find some great stories.
Some Tumblr blogs dedicated to Arthurian fanfiction might also have such stories. You can search for tags like #Arthur spanks Merlin or related tags on Tumblr. But be aware that the content quality and availability can vary greatly from blog to blog.
There's a fanfiction called 'A Different Kind of Lesson'. In it, the spanking incident is not just about punishment but also a way for Arthur to show his concern for Merlin. It's set against the backdrop of a dangerous mission where Merlin's recklessness endangers the whole group, and Arthur takes it upon himself to set things straight in his own way.
One great Arthur spanks Merlin fanfic is 'The Unlikely Bond'. It explores their complex relationship in a unique way. The story delves into the power dynamics between them while also showing their deep connection. It's well - written with vivid descriptions that bring the characters to life.
A good place to start looking for Arthur spanks Merlin fanfics is on Archive of Our Own (AO3). There are many different takes on this theme there. You can filter by tags like 'Arthur/Merlin' and 'spanking' to narrow down your search.
The banter between Merlin and Arthur in fanfiction is really interesting. It can range from light - hearted jabs at each other's habits. Merlin might poke fun at Arthur's love for jousting and how he always gets a bit too competitive. Arthur could retort by mentioning Merlin's clumsy attempts at serving him. Their banter also reflects the underlying respect they have for each other despite their different social standings. It's like a friendly sparring that keeps their relationship dynamic.
The 'Redemption' trope is also seen in some fanfictions. Maybe Arthur has made some mistakes in the past, and Merlin helps him to redeem himself. Or vice versa. It's a way to explore the characters' growth and development. And then there's the 'Battle Against Evil' trope where they fight side by side against dark forces, which really showcases their bond and loyalty.
I really like 'The Sword in the Stone' as a fanfiction - like take on Merlin and Arthur. It shows Merlin as this wise and mysterious figure guiding Arthur on his journey to become king. There are also some great interactions between the two characters that show the deep bond they share. You can find it in many libraries or online bookstores.
Merlin would likely be seen as a bit of an enigma at Hogwarts. His magic is different from the norm, so he might be a bit of an outsider at first. But his kind heart and loyalty would soon win over his classmates. Arthur would be the brave and headstrong character, perhaps a bit like a Gryffindor version of his usual self. He'd be eager to learn about combat magic and would probably be a natural leader in group projects or Quidditch teams.
It could start with a slow realization of their feelings. Maybe they were friends for a long time and then suddenly, one day, they look at each other in a new light. After getting married, they become more protective of each other. Arthur might become more open to Merlin's magic, and Merlin would be more involved in Arthur's political decisions.
During the time of Merlin's captivity, they could have long conversations that they never had before. Arthur might open up about his insecurities regarding magic and his kingdom, and Merlin could share his true feelings about serving Arthur. This would strengthen their bond in a new and unexpected way.
One great Arthur Merlin fanfiction is 'The Once and Future King's Heart'. It beautifully explores the deep bond between Arthur and Merlin in a way that feels true to the characters. The author's writing style is engaging, and it takes you on an emotional journey through Camelot's world.