typically you'd want to machine both sides to ensure flatness but it also depends on the application . If it's being counterbored and bolted directly to the table then I'd probably just face the top surface . If your planning on having threads into the mic6 then you'll want helicoils or threaded inserts , otherwise threads can strip easy or fracture the plate resulting in big chunks being broken off .
Ideally , it's worth sending it out for hard anodizing because it is a soft material . It's not necessary but it pays off in the long run if it is in constant use
mcmaster sells some nice locating pins and bushing for this sort of thing
https://www.mcmaster.com/products/lo...ating-pins-1~/