Laminate floor against fireplace brick
I would rent an &quot;undercut saw&quot; and put a diamond blade in it. Cut a channel along the floor at a suitable height. Brick cuts fairly easily and you'll have a dead-straight, perfect fit to your floor. Here's a video
You'll have to do a little creative grinding with other tools near the wall where the circular saw won't reach. You can get diamond-grit blades for reciprocating saws, or maybe go at it with some patience and a rotary tool with grinding bit.
This work is very dusty. Use a vacuum held by a helper and seal off the room.