Doing 1 cobbled climb & the finish is possible. But you have to know your way around, and it that specific part of Flanders it's not always easy with the small countryroads etc.
If you're talking about an early cobbled climb, you're talking about the Molenberg (km130; 3hours of racing to go), Oude Kwaremont (km180; 2hours of racing to go), Paterberg (km184) & Koppenberg (km190).
For all 4 climbes, you need to be there at least 1 hour before the riders. These are the most spectacular climbes so they are incredibly popular.
The advantage of The Molenberg is that this one is situated the closest to Ninove (Meerbeke, where the finish is; a 40min drive). The other 3 are 20-30km further to the south-west. With 3 hours of racing ahead, you'll have plenty of time to drive to Ninove (but be aware of the chaos there: roads closed, the RVV for women, a lot of people, hard to find a parking spot). But when you get there, you can still follow the finale live on the big screen. The disadvantage of the Molenberg is that's one of the shortest, most narrow and invisible (due to the trees & houses and the corners of the climb) climbs. And there is the obligatory traffic jam of riders & cars at the bottom of it.
The next 3 cobbled climbes are a lot better to see the riders but IMO, they are too close to the finish to comfortably drive back to Ninove (you'll spent at least 1h15" in your car and the further the riders get into the race, the bigger the traffic mayhem). Besides that, you'll miss the key moves & tactics during the race.
So is there an alternative? Yes. If I were you, i'll go see the riders on the cobbles of Kerkgate/Mater (km 135, right after the Molenberg, a nice village). It's a 3km cobblestone section that is not mentioned in the roadbook as an official climb. Well then, how come I only manage to "climb" it at a speed of hardly 14km/h?? I know, i'm not a pro; but I do know the first part of that section (before the church) is not flat at all (on the top of my head: a gradient of 9-10%). The road there is quite broad, there are few corners, so you should be able to see the peloton coming from a certain distance. It's also safe there as fences are put on the sidewalk to prevent riders to ride there instead of the cobbles. Right after this cobbled section (where the riders take a right turn towards the Wolvenberg), you need to take a left and you immediately get onto the N8 road which connects Oudenaarde directly with Brussels. Just follow that road (you'll pass the village of Brakel) and after a 40min drive you're in Ninove.