I am looking to buy a multifuel stove for my fireplace. I have removed the old fireplace surround and back panel and now have a standard size hole in my wall. There is an original slate flagstone hearth which sits flush with the floorboards (this is a downstairs room). I will need to level the back of the hole and my intention then is to put a granite or slate hearth in which will recess into the hole. My first question is; do I need to level with heat resistant concrete and to what depth also will I need to have the hearth in two pieces to allow for expansion. Thanks in advance 
