Go to your local hardware store and purchase size 2x4x10 wood studs. The number of studs you purchase is dependent on how many bricks you need to make. The studs will be used to create a ladder-like frame in which the mud bricks will set and dry, in order to hold the form.
Set two wooden studs on the ground parallel to one another. Place the remaining studs on top of the first two studs, perpendicularly. The spacing between the parallel and perpendicular studs is dependent on what size bricks you need. For example, a standard brick is 4 x 2 2/3 x 8, while a traditional New Mexico adobe brick is 14x10x4.
Attach the wooden studs together using a drill and screws. Spray the inner faces of the wooden studs with cooking spray. This will ensure that the bricks do not stick to the frame as they dry.
Purchase soil that contains a small amount of clay. Clay adds to the strength and moisture-resistant properties of mud bricks. However, too much clay will cause your bricks to crack. The amount of soil needed is dependent on the number of bricks you are making.
Dump the soil into a five-gallon bucket. Mix in a small amount of cement. Cement will increase the strength of your mud bricks. Add water until you achieve a thick, pasty consistency.
Pour the thick mud mixture into the sections of the wooden frame. Overfill each section. Use a 2x4 piece of wood to level off the top of each brick.
Allow the bricks to set and dry for two to three hours. Lift the frame off the bricks. Use a putty knife to scrape the frame clean for reuse.
Allow the bricks to dry for three days. Then turn each brick on its side. Allow the bricks to dry further, sitting on their sides, for three more days. Once the bricks are dry, use a putty knife to scrape and shave uneven and excess mud from the sides of the bricks.