Growing Shiitake on cut logs- Where to inoculate?

I am growing Shiitake mushrooms on a recently felled oak.  I have the logs split in half.  I coated the flat sides with beeswax to seal in moisture.  I plan on inoculating with a drill bit and sawdust spawn, sealing with wax.  Please review the photos.  My question is- Where should I drill into the logs?  On the flat sides or the bark side?  Would it be good to drill sawdust spawn into the flat side that will be face down on the ground?  Any advice would be greatly appreciated.            

~Jim Majeski
Westport CT