First, I built the mold with wood panels and aluminum sheets on the bottom (as the top side of the counter top) so that the finishing surface on the top would come out perfectly smooth.
There were two layers of rebar inside this 2.5 inch deep mold and well positioned to reinforce the strength of the concrete. Special reinforcement was added to the opening of the sink as well.
Quikrete® Non-Shrink Precision Grout was the cement that I used and only mixed with water. I also added some red pigment during the mixing and it came out with somehow warm but light red color.
Curing is very important for concrete casting especially when there is only cement used. I used wet towels to cover these babies and watering them everyday for over two weeks.
After the molds were removed, I used very fine sand papers to wipe out the residue, and later sealed them with sealant and bee wax on the clean surfaces as waterproofing. Be sure to use non-toxic water-based sealant since the food will be touching the concrete.