23-year-old, Birmingham-born Flanagan, a product of Walsall FC's Academy, rose through the ranks at Banks's Stadium and turned professional in January 2013, earning particular praise from then-academy boss Neil Woods.
A central midfielder by trade, Reece would make just under fifty first-team appearances during his time at the club and also enjoyed a successful loan spell with his new parent club, scoring a couple of memorable goals.
Flanagan spent time on trial with Tranmere Rovers and Grimsby Town over the summer but was unable to land a deal, until he came to terms on a contract with the Brakes earlier this week.
Reece has found his match minutes hard to come by over recent seasons and missed the entire 2016/17 campaign after rupturing his anterior cruciate ligament, before dislocating his shoulder during his comeback game ten months later.
Leamington boss Paul Holleran, speaking via his club's official website - LeamingtonFC.co.uk - welcomed the opportunity to sign Reece and insisted the former loanee is capable of making an impact in the side.
He said; "I'm delighted to be able to bring Reece back to the football club. He made a significant impact when he was first with us on loan with us four years ago, and is a very talented player.
"He's had a tough time with injuries but he's still in the early stages of his career and is more than capable of making a contribution for us at this level. He's been training with us a bit so we've decided to get him in on a permanent basis and see how he gets on.
"He's full of flu at the moment, so may not be involved when we travel to Ashton United on Saturday, but will hopefully be involved very soon."