The Munster veteran twice attempted to make comebacks last term, first against Toulon in October and then against Ulster in January, but on both occasions he succumbed to injury yet again.
Flannery hasn't played for close to six months but Declan Kidney included him in Ireland's pre-World Cup training camp.
The 32-year-old says the first week in Carton was as successful as he could have hoped but he remains cautious about his chances of returning action in time for the summer friendlies and the global gathering in New Zealand that starts in September.
"I have to be very cautious because there is still an imbalance between one leg and the other and I won't believe I am okay until I have come through at least one full match. I have come back several times already only to break down," Flannery, who missed the 2009 Lions tour through injury, told the Irish Examiner.
"It was a good week up in Carton and there are still a good few weeks still to go. I have put the foot to the metal in each of my attempts at recovery up to now and there have been a number of setbacks.
"The medical team have been tremendous with me and very patient but we are determined to take things slowly. I'm still favouring my right leg and that is something we are working on. It's a case of trying to wake up the left leg."