Dig a 12-inch deep hole for the foundation of your brick smoker. Remove the soil from an area of 40 inches by 40 inches with a shovel. Add 2 inches of sand and spread evenly. Fill the hole with gravel and then top with sand. Brush the sand over the gravel until the sand is even with the surface of the ground. The sand will hold the gravel solidly in place.
Build a 40-by-40-inch frame with 2-by-4 lumber, securing it at the corners with screws. Measure the distance from corner to corner and straighten until both diagonal measurements are equal. Set on top of the sand and gravel foundation.
Mix a bag of ready-mix concrete -- enough to make 3 cubic feet -- in a wheelbarrow with enough water to make a sludgy mixture. Use a garden hoe to mix the concrete. Pour into the wooden frame and level with a 2-by-4 to make an even surface.
Mix up a batch of mortar for setting the bricks in place. Use just one-quarter of a bag of mortar and make more as you need it. Use a bucket to mix the mortar with water, mixing it together with a trowel.
Butter the bottom of a brick with 1/2-inch of mortar. Set the brick on the concrete base. Butter the bottom and end of the next brick and set next to the first brick. Continue to add the bricks along the perimeter of the base, leaving a 3/8-inch gap between the bricks filled with mortar. Scrape off the excess mortar and check the level of the bricks often, tapping them with a mallet as necessary. Stack the bricks 12 inches high. Dry for 48 hours.
Fill 8-inches of the interior of the bricks with sand. Fill in the top 4 inches with concrete. Dry overnight.
Cover half of the concrete base with three layers of brick around the perimeter and across the center, mortaring each brick. Fill the center with concrete. This will be the base for your smoker portion of the structure.
Stack the bricks around the perimeter of the fire side of the smoker to match the height of the smoker portion base. Leave 1-inch gaps between six bricks on the bottom side layer to allow for ventilation.
Stack another six layers of bricks around the perimeter of the entire smoker, using mortar between each brick. Leave 1-inch gaps between the outer side of the top layer of bricks over the cooking side.
Lay bricks down the middle to give extra support. When laying the bricks for the center wall, leave 1-inch gaps between the top layer of bricks so the smoke will enter the cooking chamber.
Cover the top of the smoker with two steel doors. Order them to size and with hinges on one side and a handle on the opposite side.