Fireplace brick must be laid in a specific way for safety and proper installation. The first step is to prepare the fireplace stand by making sure that it is level and sturdy enough to support the weight of the masonry surrounding your firebox opening. If you are planning on laying new bricks, then clean out any ash or debris from inside the firebox before proceeding.
First, lay down refractory mortar on bottom layer of bricks with a margin around all sides so as not to get any mortar between them and stucco over walls will adhere better if there’s no sticky mortar holding everything together. Second attach metal lath strips directly across surface about every two feet horizontally along base row which will hold back mortar when installing next course of brick. Apply mortar to the second course brick in same way, but this time use a steel trowel with narrow edge. Use it to force mortar in between each brick so that there are no spaces and all joints are filled solid. Once you have finished laying down your bricks, allow them at least 24 hours to dry before using fireplace or applying grout.
Make sure when cleaning out for installation of new firebrick that you deal with any residual ash still left behind after making sure everything is clean sweep up dust thoroughly by either sweeping or vacuuming make sure nothing gets into the fresh mortar while setting like hair paper clips etc which can cause unwanted consequences later on be aware where lint goes if vacuumed carefully remove loose debris from inside the firebox if possible to avoid problems with mortar setting when you’re done it will be safe to light your fire again.