Clear out all of the objects within 36 inches of the Franklin fireplace or stove. Even if you have a small room, the area around the fireplace needs to be free from furniture or clutter.
Cut a piece of fireproof millboard to fit under your Franklin fireplace if you do not have it installed on a stone fireplace hearth. Measure the width and depth of the stove and add at least 24 inches to the depth (6 for the back and 18 for the front) and 12 inches to the width (at least 6 inches extra on either side). Use these numbers as the size of your fireproof millboard.
Lay the millboard on the floor in the position where you plan to install the Franklin fireplace. Drop a sheet of 24-gauge steel over the millboard. These layers will prevent any sparks or coals from possibly igniting the floor boards.
Cover the steel with 1-inch clay tiles. Set them in place without mortar to find a pattern you like and then use mortar to cement them together on the bottom and the sides. Use a trowel and leave 1/4-inch gaps between the tiles.
Frame out the edge of the tiles with wood molding and trim nails to finish off the hearth. This framework along with the weight of the tiles and stove will anchor the millboard and steel to the floor.