Fireplaces, Heating Stoves, Flues and Chimneys - Hearth Stones

Hello,
I am putting a fireplace in our basement. it is a kozy heat 3 way fireplace. It currently sits about 18 inches off of the floor. The 18 inches below the fireplace we want to place stone on with a hearth stone directly below the unit itself. I would like the hearth stone to stick out about 10 inches around the fireplace. My question is, how do you secure the hearth stone? Currently there was a box made 18 inchess off of the floor below the fireplace. (fireplace sits on this) It was built using the same dimensions as the fireplace.
Any assistance you could provide would be excellent.
Thanks.

i would use some nonshrink grout, mixed to manufactures specs, is this a one piece stone or are you going to piece this together? if piecing together use some masonry cement as a grout between each stone and remove splatters immediately then wipe down with a weak acid to remove the cement film from the surface.

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THanks for the reply.

Maybe this will help explain a little.

Here is a picture of the fireplace in question:
fireplace on Flickr - Photo Sharing! (http://www.flickr.com/photos/25179547@N03/3090794702/)

Here is the hearthstone we were looking at having. I would cut this in half to have a 10" chunck. We would like to use this if one may want to sit on it but mainly to force a little distance from the fireplace when our son starts walking to keep his little hands away from the unit.
http://www.gaf.com/Content/STONE/RES1/STONE/cr_hearthstone.jpg

Below the above chunk of stone we are going to place an aspen type stacked stone.

Does that change your answer at all or would using masonry cement work to hold this against the plywood?

THanks again. I hope the images work.

if you are going to use the stacked stone under the hearth stone then just use the masony cement to hold everything, it will help to use some wire mesh screwed to the plywood and extended out into the stone layers to help keep it from seperating away from the plywood, or use wall ties used with bricks fastened to the plywood and extended into the stone layers. just don't extend them out to the outside.

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The process i was going to go through in installing the stone was to put some roofing felt down first stapled to the plywood. Then use galvanaized nails to fasten my 2.5 lath to the plywood. install a scratch coat and then place the stone on to that.
The wire mesh you speak of, is the lath the same? Also, masonry cement is that the same as mortar?