The television presenter, who won the 2014 series of the BBC One dancing competition, took her own life in February of this year.
The programme, which will celebrate past Strictly winners, will feature a tribute to Flack.
She won the glitterball trophy alongside professional dancer Pasha Kovalev in 2014.
Strictly: The Best Of The Final will also “celebrate the finalists, the emotion and the incredible routines” that have featured in the last round of the competition, according to the BBC.
The programme will be hosted by Tess Daly and Claudia Winkleman, and judges Craig Revel Horwood, Motsi Mabuse, Shirley Ballas and Bruno Tonioli will also reminisce about previous finals.
Other specials including The Best Of Movies, The Best Of Blackpool and The Best Of Musicals will also be broadcast by the BBC.
Strictly: The Christmas Countdown will also air over the festive period.
It will feature the 25 most memorable dances in the programme’s history, as voted for by viewers.
The BBC is yet to announce when the episodes will air.
