What is the best technique for creating a knockout for an undermount sink for a concrete countertop form? I’m in the process of building the form.
I have an undermount porcelain sink that I want to use with a concrete countertop. I have a paper template for the sink, but it seems like it may be a little tricky to get a really clean cut in a piece of foam board that will look nice. All I can think of is to use a jigsaw and follow the template (attached to the foamboard) as best as I can. Alternatively, I'm thinking that maybe there's a way to use spray on foam to the actual sink to build a mold. I’m thinking the ID of the sink is exactly the size of the knockout, so the concrete would be flush with the edge of the sink.
looking for ideas! thx