DIYbanter - Where/how to fit a hearth

okay,okay, so the obvious is "in front of the fireplace" :-)

We've just had an engineered wood floor laid (3mm oak veneer on 15mm
softwood substrate) and I removed the hearth before the floor was put down
to avoid the fitter using quadrant, or generally making a pigs ear of
cutting around it. The flooring covers the whole floor (including the part
where the hearth is going to be.

The hearth is sold 3" limestone (about 100kg) and I am in two minds weather
I should just pop the hearth down on the floor, or if I should mark out
where the hearth is going to be and carefully cut a section from the floor
so the hearth will drop in.

Pros of just popping on the floor is that it is minimum work, and no
precision cutting required; drawbacks are that it might not be safe (though
I can see how), but I am more concerned about the weigh of it warping the
floor over time

Cons of removing the section of floor to fit the hearth is that I then have
to make very neat and precise cuts (I am sure Saturday morning with the
router would be just fine) and that I am then susceptible to making a crap
job of it.

Any thoughts?

P.s. My last posting was about adhesives for skirting boards. I bought the
gripfil in the end, and it works an absolute treat, even holding it all in
place despite the wibbly-wobbly walls we have...

Cheers
Chris