Looking at all the schedule, the following games are eligible for flexing:
Week 13 – 11/30 – Seahawks @ Cowboys
Unless the Cowboys totally tank (one can hope), I don't see this getting flexed
Week 14 – 12/7 – Patriots @ Steelers
Patriots and Steelers are both high profile teams, I can't see this one being flexed either
Week 15 – 12/14 – Chargers @ Raiders
Although this could end up being a really good game to watch, I would say that outside the AFC West, it might not be that popular nationally, so it's on my radar as a high likelihood of being flexed
Week 16 – 12/21 – Saints @ Rams
One or both of these teams will be pretty bad by this point in the year. This game will likely be pointless. Not as high a chance as the Raiders/Chargers, but I'd rank this behind it and the Jets/Browns
Week 17 – 12/28 – Jets @ Browns
Jets are in NY and will have the national treasure (wait while I try not to throw up) Rodgers at QB and the Browns may be in the playoff hunt, but they usually find a way to screw things up. This game IMO, has a high likelihood of being flexed out. Being so late in the year, there should be more intriguing options, but still I'd rank their odds 2nd to the Chargers/Raiders
Of course there's always the option of not flexing any games. Just because the rule is there doesn't mean it'll be used. 28 days in advance is a long time to try to decide if a game is going to be good or not and to try to find a better matchup. A lot of things can change in a month.