Here are the steps to make concrete countertops:
1. **Build the Mold**: To determine the size of your countertop, measure the base cabinets that the countertop will be sitting upon. Add an extra 3/4" for each overhang. Start with a 4' x 6' piece of 1" thick melamine particleboard. Set it firmly on a pair of sawhorses. Measure and mark the exact dimensions on the mold base, then cut to your dimensions using a circular saw. Cut the sides of the mold.
2. **Make Cutouts**: Make cutouts in the mold for the sink and faucet. Use silicone caulk to seal any joints.
3. **Build Support Frame and Prep Wire**: Build a support frame out of 2x4s to hold the weight of the concrete countertop. Cut wire mesh or rebar to fit inside the mold, then place it on top of the support frame.
4. **Mix and Pour Concrete**: Mix concrete according to instructions on the bag and pour it into the mold.
5. **Remove the Mold**: After 24 hours, remove the mold.
6. **Finish the Slab**: Polish with diamond tooling.
7. **Install the Countertop**: Install your new concrete countertop onto your base cabinets.
