Granite on concrete slab question

Let me start by saying I know nothing about granite. What I would like to do is lay a piece 55"L x25"W x4"D in front of my outdoor flagstone fireplace as a hearth.I have grey bricks around the face so I'm thinking it won't look too out of place with all that flagstone. I poured a 2x6 pad today at the same dimentions to ground level today and planning to set the granite on the pad once it dries and I convince my buddy to help me move 500+ pounds to my house. It seems to me it would need something between the two surfaces as a barrier, maybe thin set mortar or whatever, does not seem like 500#s would move or shift but I'm in Illinois so I want to be sure because I sure don't want to move it again once it's set. Any help appreciated

I think something as simple as silicon caulk would do the job. That's how granite countertops are connected to the cabinets. Just a couple beads, or a zig-zag would be all you need. Sure you could use thinset as well, but at a higher cost and mess.

Silicone would probably work for a while but I would think thin set or mortar especially would be the more prefered avenue. Heck any more they want you to set you tub in a bed of grout, not the worst idea. I am wondering if that is due to the skimpy manufacturing process or just good sound advice. Either way silicone at ground level with a slab of granite on it mmmmmmmmmmm not so much. I would mix up mortar and be sure to tuck point ALL edges. I live in WNY and wet snow and freezing temps are not your friend, you need to keep the water from getting under the granite. 55" x 25" x 4" seems like a 5 gallon pail or so of mud not hardly any cost and very little mess, much better job!
Best of luck!

I strongly suggest thin set also. Depending on the color of the granite, you might want to use the white thin set. Make sure to use the correct size trowel tooth size.

I'm voting for the silicone.

I think the issue isn't holding the stone in place as much as keeping water from freezing below it and either causing the stone to crack or heave. So I vote for some form of mortar applied over the entire area under the stone rather than beads of silicone caulk. This is all assuming that the concrete pad it rests on doesn't get water freezing below it.

Thanks for the replies, I too think mortar is my best bet, but maybe with a slight variation, after doing a lot of Google searches I found someone doing a somewhat similar project and they were advised to use an acrylic latex additive to the motor instead of water to increase the bond strength and minimize water penetration. They mixed it to a consistency of cake batter and applied with a square groove trowel. I'll check out the stores see what they have. First I need to get a grinding wheel and smooth out the flagstone 4" above the pad to get a good fit up to the fireplace.