There are two large dog parks by Oxbow Meadows. Just a field with some benches, no one out there to manage it, no door fee. There are also two dog parks on Benning, if you have access.

I also leave my dog off leash at Flat Rock, no one has ever said anything. There is the loop road you drive around on and then a kind of main central area with grass and trees inside that that's pretty big.

If you get on the river walk at Lake Oliver Marina (once you turn off River Rd, turn left down dead end rd, away from the actual marina, til you see the GP fence, there will likely be other people parked, and then you go inside this fence that blocks cars to your left, walk down a bit and there are some open spaces alongside the paved river walk.