How to prepare a rough concrete slab for pavers
My pa did a rather extensive paver back patio with curved steps, concentric pavers, a retaining wall and other challenges.  It looks beautiful.  Some of it is laid on existing concrete, some on packed gravel before the sand.  He used masonry mortar and concrete fill for the steps and edge pieces and it has definitely stood the test of time.  As mentioned in AlaskaMan's comment, the thickness of mortar allows you to lay the section in sand first and match the edge to the height of that.  After 25 years a small section of the lower patio has sunk about 3/4 inches because the gravel wasn't packed hard enough, but otherwise the whole thing is rock solid including parts without concrete base.  It will also deal with the unevenness of your pad, which to my eye does look like asphalt, as isherwood suggests.
One other note if you lay brick over solid pads, any drainage problems that exist with the pad will continue to exist under the sand.