I am trying to apply maven to an existing project which already has a directory structure in place. All I can find from previous question is the following.
Maven dir
I guess you need to have something similar to below.
Seeing WEB-INF, I assume you want to build a war. Maven war plugin does this. You will need to configure this a bit since the folder structure is non-standard - for instance you may need to specify the location of web.xml using webXml property. These are documented in the usage page.
src-java
...
src-properties
...
org.apache.maven.plugins
maven-war-plugin
WEB-INF
...