Be conservative in your time estimate so that you do not rush and cut corners. Clay paving brick can be set in a sand base that is supported by a crushed gravel base. They can also be permanently attached to a poured concrete base. Moles can push up brick, and ants love to bring sand to the surface between the joints. This sand is then often tracked back into the house.
Weed control is a constant problem as well.
Installing the brick with cement mortar over concrete eliminates all of these problems. The amount of work to do both methods is nearly identical. In both instances you will need to excavate and remove soil to create the area for the gravel or concrete base. Transporting the gravel or concrete via wheelbarrow to the patio site requires the same amount of work. Installing the base materials is also very similar.