One popular 'Star Wars Anakin slave' fanfiction is 'The Slave Boy's Destiny'. It delves into Anakin's early days as a slave on Tatooine and how his experiences shaped his character. It shows his relationship with his mother in more depth and also his first encounters with the Force in a very different light than the movies sometimes portray.
A lesser - known but really interesting 'Star Wars Anakin slave' fanfiction is 'Slave to a Greater Purpose'. In this one, the author takes a unique approach by highlighting the skills Anakin learned as a slave, such as his mechanical aptitude and survival instincts, and how those skills became assets when he entered the world of the Jedi. It also has some great scenes that show his loyalty to his friends, which was deeply rooted in his experiences as a slave.