We bought a beautiful piece of rock yesterday - NY Bluestone. It is such a gorgeous hunk - I felt like we had a VIP in the back of the car when we driving around town! It will be used for the outer hearth. Before we could cement it in place, we needed to bring up the level of the front wall (on top of the cement blocks). We made a plywood form, attaching it to the block with some tap-cons, then poured concrete over some old bricks. We stuffed polyester stuffing (used for making toys) into the air space between the concrete block wall and the floating hearth slab. I used my new favorite thing - aluminum tape - on top of the stuffing and against the firebricks bricks to help release the form.