If the slab is the same size as a multiple of whole bricks including mortar joints lay the border first then start setting brick at the border as shown on these pages.
How to lay brick floor in backyard.
Building a brick floor or patio over dirt is not as simple as flattening the ground and laying down bricks.
Run a tamper over the patio to set the bricks.
If the slab has control joints start along the control joints and work toward the edges.
Soak the patio with a gentle spray of water to help settle the sand into the gaps.
Then install a border of wooden boards or brick pavers lay down a layer of sand and level.
Before you lay any bricks plan the patio layout.
Next lay down gravel or crushed rock to solidify the foundation and cover the top with landscaping fabric to prevent weeds.
An outdoor space made with patio pavers can withstand heavy foot traffic and needs little maintenance.
Repeat the process until the sand fills all the gaps.
You can choose stone travertine brick or concrete pavers for your patio.
With the right steps however a brick floor over dirt can last for decades.
Spread a thin layer of sand over the entire patio and use a push broom to work it into the gaps between pavers.
If the ground under the bricks is not properly prepared the bricks will quickly move out of place succumbing to erosion as the ground beneath them wears away.