How do I create an executable fat JAR with Gradle with implementation dependencies?

You can use the following code.

jar {
    manifest {
        attributes(
                'Main-Class': 'com.package.YourClass'
        )
    }
    from {
        configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) }
    }
 }

Be sure to replace com.package.YourClass with the fully qualified class name containing static void main( String args[] ).

This will pack the runtime dependencies. Check the docs if you need more info.