Configuring slf4j and log4j correctly on WebSphere 8.5 - log4j

Question

WHat's the correct way to configure slf4j + log4j on WebSphere 8.5.
My approach was:
* Include slf4j-api in WEB-INF\lib of the war files of the applications
* Include the binding ja slf4j-log4j in WebSphere lib
* Include log4j.xml in JVM classpath external to the war file.
Only problem is that it doesn't work. It fails with an error on initializing.
Guess my approach is wrong?
Thanks for any assistance!
Here's the stack trace. Note that slfj-api is found in WEB-INF\lib of the WAR file:
Caused by: java.lang.NoClassDefFoundError: org.slf4j.spi.LoggerFactoryBinder
at java.lang.ClassLoader.defineClassImpl(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:295)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:154)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:711)
at java.net.URLClassLoader.access$400(URLClassLoader.java:92)
at java.net.URLClassLoader$ClassFinder.run(URLClassLoader.java:1159)
at java.security.AccessController.doPrivileged(AccessController.java:314)
at java.net.URLClassLoader.findClass(URLClassLoader.java:594)
at com.ibm.ws.bootstrap.ExtClassLoader.findClass(ExtClassLoader.java:204)
at com.ibm.ws.bootstrap.ExtClassLoader.loadClass(ExtClassLoader.java:116)
at java.lang.ClassLoader.loadClass(ClassLoader.java:690)
at com.ibm.ws.classloader.ProtectionClassLoader.loadClass(ProtectionClassLoader.java:62)
at com.ibm.ws.classloader.ProtectionClassLoader.loadClass(ProtectionClassLoader.java:58)
at com.ibm.ws.classloader.CompoundClassLoader.loadClass(CompoundClassLoader.java:616)
at java.lang.ClassLoader.loadClass(ClassLoader.java:690)
at com.ibm.ws.classloader.CompoundClassLoader.loadClass(CompoundClassLoader.java:584)
at java.lang.ClassLoader.loadClass(ClassLoader.java:690)
at com.ibm.ws.classloader.CompoundClassLoader.loadClass(CompoundClassLoader.java:584)
at java.lang.ClassLoader.loadClass(ClassLoader.java:690)
at org.slf4j.LoggerFactory.bind(LoggerFactory.java:121)
at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:111)
at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:268)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:241)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:254)
at no.klp.minside.handler.SoapLoggingHandler.<clinit>(SoapLoggingHandler.java:28)
at java.lang.J9VMInternals.initializeImpl(Native Method)
at java.lang.J9VMInternals.initialize(J9VMInternals.java:236)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:80)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:57)`enter code here`
at java.lang.reflect.Constructor.newInstance(Constructor.java:539)
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:110)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:280)
... 113 more
Caused by: java.lang.ClassNotFoundException: org.slf4j.spi.LoggerFactoryBinder
at java.net.URLClassLoader.findClass(URLClassLoader.java:599)
at com.ibm.ws.bootstrap.ExtClassLoader.findClass(ExtClassLoader.java:204)
at com.ibm.ws.bootstrap.ExtClassLoader.loadClass(ExtClassLoader.java:116)
at java.lang.ClassLoader.loadClass(ClassLoader.java:690)
... 147 more