Flockhart returns to Scotland having spent last season on loan at French Federale 2 club, Stade Nicois.
The 20-year-old Number 8 had previously played for Glasgow Hawks in the Premiership and was also a member of the Scotland U20 squad that recorded a best-ever finish at a World Rugby U20 Championship in Georgia last summer.
Standing at 6ft 5in and weighing 108kg, Flockhart attended Strathallan School along with current Warriors George Horne, Matt and Zander Fagerson.