For these particular countertops we decided to go with a cast in place process (we build, pour, polish, and seal the countertops on site) instead of the normal precast method where we build them in our shop and deliver them since there were some clearance issues that prevented us from doing that.
That said, for our concrete farmhouse sink we only have one option – precast. It is impossible to try to do this as a cast in place option. The sink itself was made in a separate mold, poured, cured, then installed underneath the countertops once they had been finished. All pieces were sealed with a solvent-based polyurethane that added a high-gloss shine and made the surfaces very durable and stain-resistant.