The final steps in our “how to make a countertop out of concrete” project was to mix up the cement, pour it in, pack it along the edges, level it, trowel it to smooth it out, and seal it with a water based polyurethane sealer. Voila! The countertops came out spectacularly. Concrete countertops with their richly varied finishes create a beautiful and truly unique centerpiece for any kitchen, bathroom, or exterior area.