19-year-old, Stoke-on-Trent born Slinn is a product of the Port Vale youth system and rose through the ranks to sign his first professional contract in February 2017. He enjoyed loan spells with Stalybridge Celtic and Rushall Olympic during his time at the club, earning plenty of plaudits from those around him.
Despite signing an 18-month deal which included an option for a further year, Slinn was released by Vale at the end of last season and has spent the last few months seeking to attract interest from a new club.
Slinn, who is expected to form part of Walsall's development side whilst also serving as cover for Liam Roberts and Chris Dunn, will immediately link up with former club Rushall Olympic on loan as Dean Keates looks to secure first-team football for some of the squad's fringe players.