Where is the best place to sell my Jeep?

Assuming you are willing to communicate and meet with strangers, FB Marketplace and Craigslist will get you lots of views. Avoid autotrader.

You can post it for sale here
 
Completely depends on the Jeep and the intended audience. An all original very clean rust free YJ - bring a trailer or similar. A woods beater, craigslist or FB marketplace, something in-between (modified but not a beater), depends on the details and value.