Cut and Reinforce the Sink Cabinet
Measure and mark a centerline on the sink cabinet front, then measure outward from this line to mark the sink opening. The cutout should be 1” smaller than the overall surface width of the sink to ensure that the sink lip will cover the cut.
Use a reciprocating saw to cut the opening (Image 1). Turn the blade upside down in the saw so you can see the action for a more exact cut.
Install L-brackets, shelf brackets or wood supports cut to fit to the interior cabinet stiles and back to create a support frame for the sink. Position the brackets under the sink lip to carry the weight (Image 2).
Dry fit the sink into the cabinet opening (Image 3). Its lip height should be equal to the thickness of the new countertop.
The cabinets on both sides of the sink also need to be reinforced to carry the extra weight of the butcher-block countertop. Place wood blocks, cut to fit, in the corners and attach them with glue and screws.