Here's my take on the subject.
   I like clearance for mine so I can flatten the backs and not have 
knuckle dragging trouble.
The bevel counts but its really all about the back.

  I like to clamp it securely in a vise so I can put some pressure on 
and not have to chase it around.

   So I make my boxes with a thick bottom. A 2X4 is enough.
The sides come up only about 1/4" . Just enough to trap the stone.

   Lid is optional, but it keeps the dirt off.
http://users.snowcrest.net/kitty/sgrandstaff/images/hometools/stonebox4.jpg
http://users.snowcrest.net/kitty/sgrandstaff/images/hometools/stonebox7.jpg
http://users.snowcrest.net/kitty/sgrandstaff/images/hometools/stonebox8.jpg

Oh and dished stones? I just pick a spot of relative flat cement and 
plop on down with a glass of water.
Last time it was my back porch step. There was a small area of slight 
roughness. (the cement finisher was not that bad, but still left a bit 
to be desired lol)
  In about 10 minutes I got a flat stone and slightly smoother cement.
  http://users.snowcrest.net/kitty/auction/step.jpg
yours scott

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*******************************
    Scott Grandstaff
    Box 409 Happy Camp, Ca  96039
    scottg@s...
    http://www.snowcrest.net/kitty/sgrandstaff/
    http://www.snowcrest.net/kitty/hpages/index.html