You might be able to flat tow your 2018 Explorer, but it depends on what engine and drivetrain your Explorer has. First off, your Explorer needs to have two-wheel drive (rear-wheel drive). If it passes that test, it also needs to have either a 3.5-liter or 3.7-liter V-6 engine**—if so, your Explorer is in the clear for flat towing.
If you have an all-wheel-drive Explorer or one with a different engine, don’t flat tow it under any circumstances, as doing so can damage the drivetrain.