This is pretty similar to the Copying direct dependencies example. The difference is that the direct dependencies are unpacked, including the transitive dependencies. To unpack the artifacts, use the dependency:unpack-dependencies mojo and configure the dependency plugin to something like the sample below:
<project>
[...]
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack-dependencies</id>
<phase>package</phase>
<goals>
<goal>unpack-dependencies</goal>
</goals>
<configuration>
<includes>**/*.class</includes>
<excludes>**/*.properties</excludes>
<outputDirectory>${project.build.directory}/alternateLocation</outputDirectory>
<overWriteReleases>false</overWriteReleases>
<overWriteSnapshots>true</overWriteSnapshots>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
[...]
</project>