The base configuration is really (too) simple

    # Load balancer creation
    <Proxy balancer://phpfpmlb>
        BalancerMember fcgi://10.0.0.12:9000
        BalancerMember fcgi://10.0.0.34:9000
    </Proxy>
    # Redirect PHP execution to the balancer
    <FilesMatch \.php$>
        SetHandler "proxy:balancer://phpfpmlb"
    </FilesMatch>

For more information, read the documentation: