I2S audio

I would like to know how to take advantage of the Nanopi M3's support of
5ch audio out over the 7 I2S pins.  I am trying to find a way to add
speakers to my Nanopi M3 setup using an internal connection (within the
space of the board) and the I2S looks to be the only option (the 3.5mm is
external).  I am thinking I can use the MAX98357A audio amplifiers from
www.adafruit.com to connect directly to the I2S pins and thus gain an
internal speaker connection (mono only).  But I'm not sure if this is the
intended solution for audio out over I2S. 

I haven't been about to find a pinout diagram for the M3's I2S pins to
properly figure out how to make this setup.  Is there a pinout diagram
available for the I2S pins?