I' d like to see a pict ,make a few posts and after you will reach 10 posts
Then the posting of attachement and web links should work
It's quite possible to reach the accuracy you want, a dadoo not necessary
gluing is a must for it could not move.
The side looking at saw must be perfect flat one piece, no assembly this side
You may use screws for assembly while glue dries up but then got to recess
them and use a wood filler , sand it flat.
a 2x2 never is square, or never really stays in time.