Install the next three bricks at the opposite end of the slope. This allows for running a string line from one end to the other, helping keep the bricks level and plumb. Carefully butter each brick with a thin layer of mortar (Image 1) then place each brick carefully, ensuring they are level and plumb. Follow the chalk line as the reference for the top surface of the bricks. (Image 2).
Another way of establishing a guideline is to create a three-dimensional representation of the blue chalk line (delineating the proper height of the bricks) by essentially extending that line out with string. Place two cinder blocks on each end of the counter unit base. Then take a string line and extend it between the cinderblocks on either end (Image 1). This creates a reference-line for both the height and front-edge dimension for laying the rest of the bricks (Image 2).
Use a concave jointing tool to smooth the mortar lines between the brick. This specialized tool (Image 1) allows you to give a consistent shape to each section of mortar while removing any excess (Image 2).
Consider using bricklayers’ tongs to help you carry bricks when working on a project like this (Image 3). This handy tool won't lighten your load, but it makes carrying several bricks at once from place to place on your work site much less cumbersome.