How do I cut a brick fireplace hearth to allow for a laminate flooring expansion gap?
While this will not directly answer your question, I'd like to offer an alternative solution.
Modify Existing Molding
If it were me. I'd get some transition molding, with a profile like this.

I'd then set up my table saw to rip the piece, to remove the angle profile on the back edge.

Which would give me a profile like this.

Once I had my molding ripped to size, I'd create a border around the hearth using 45° butt joints.

When installing the flooring, I'd stop short of the hearth to compensate for my expansion gap and the thickness of the moldings leg (the piece that hangs down). Once the flooring was installed, I'd install my molding.

The molding allows the floor to expand and contract, while also providing an attractive transition between wood and brick.
Note: If you match the molding color to the flooring color, the transition will be less noticeable.