This is the second post on the countertop that I’m creating for my townhome. See the photos below for its progress.

Gaps and cracks were filled with an epoxy resin. I used some masking tape to contain the resin.
After the resin hardened I used a orbital sander to remove excess resin.
Here you can see that all gaps are filled. The boards are now one unit.
I used a hole saw and a circular saw to cut out the hole for the sink.
A perfect fit! The sink was removed so I could add a finish to to the wood boards.
A beautiful finish!