I cannot afford another winter using propane as my only source of heat. I want to install a cast iron fireplace insert. But I cannot find a 2 sided insert. In-fact I don’t even think they make 2 sided wood burners. I’m probably going to buy one this week. But I’m not sure how to safely seal off the second side of my fireplace. See attached photos; I could really use some help on this. Edit: Should I do the stone work before or after installing the insert?