Excavate an area 24" wider and 8" deeper than the length and combined widths of the grill and counterboard you will use. Dig to a depth of about 4", keeping the edges as straight as possible.
Place the prepared concrete mix in the excavation as a footer. Screed and float. Damp-cure the concrete for 3 to 4 days.
Dry-lay the first course of blocks on the footer to determine their correct placement. Begin at one end, interlocking the sidewalls with the back wall. Mark the location of the blocks on the footer.
Lay a 1/2" bed of surface bonding cement on the footer and set the first course in it, beginning at the same end and butting the blocks together. Make certain that this course is set straight and level.
Stack the remaining block in a running bond pattern, interlocking all the walls together. Stack the grill walls 5 courses high, and the counter walls 4 courses high, making certain to place them plumb on the course below.
Place the steel hangers in the grill sidewalls after the second, third and fourth courses; place them in the counter sidewalls after the third course.
Mix as much surface bonding cement as can be used in about an hour and apply a 1/8"-thick coat to completely cover the wall surfaces. After 8 hours, mist the barbecue with a fine spray. Repeat this several times daily for 2 to 3 days moist-cure