Clean the area where you are going to install the fireplace. If necessary, use a soap and water solution to remove any soot or debris.
Using painter's tape, mark the dimensions of the fireplace against the wall and on the floor in front of the wood stove.
Place the metal lath on the floor. Using a utility knife, cut the lath to match the dimensions on the wall and the floor. Remove the painter's tape. Nail the lath securely into place.
Set out the bricks in a rough approximation of the finished fireplace, to ensure that you have an adequate supply. Measure for any cuts that may have to be made to the bricks to fit the desired shape of your fireplace. Double check your measurements before making any cuts. Make any necessary cuts to the bricks using a diamond-bladed wet saw.
In a mortar pan, combine the mortar according to package directions. Stir water into the mortar until it has the consistency of cake batter and is thoroughly mixed. Apply a layer approximately 1/2- to 1-inch thick using a trowel on the bottom and back of a low-lying brick. Affix the brick into place.
Continue upwardly building the base layer of bricks, setting them about 1/2- to 1-inch apart. Keep mortaring and laying bricks in layers, smoothing out the mortar with the trowel between bricks if necessary, until the fireplace is built to the desired dimensions. Generally, a fireplace is two to four feet high, but you can continue building the brick right up to the ceiling for an authentic look.
Wipe away any excess mortar. If the metal lath is showing in any spots, cover the lath with a layer of grout. Install the remaining bricks on the sides and bottom of the fireplace. Drying time for the mortar varies by brand. Allow to dry according to manufacturer's specifications.
Allow the mortar to dry at least overnight before applying any grout. Mix the grout according to package instructions. Grout the fireplace using a grout float. Deeply push the grout in between the bricks to fill the gaps. Use a wet sponge to wipe any excess grout away. Let the grout dry 24 to 48 hours before building a fire.