To do this, install the miter bolts as shown in Photo 5 and then slide the top into the corner for a test fit. Before you scribe, align the front edges of the countertop parallel to the cabinet fronts. Close gaps where the backsplash meets the wall if possible. Scribe the top as shown in Photo 6. Keep in mind you can remove up to 1/2 in. from the backside of the backsplash to fit your wall. This is more than enough in most cases, so don’t panic if your adjoining wall looks out of whack.
Next, sand down the back edge (Photo 7) of the backsplash to your scribe line with a belt sander. Tip the belt sander slightly to undercut the backsplash for a tighter fit. Set the countertop back against the walls and check it for fit. It should fit on the first try, but you may need to do some additional sanding for a tight fit.
Next, remove the miter bolts and separate the sections so you can cut the sink opening (Photos 8 – 10).
Tip: Be sure you have a build-up strip under the backsplash behind the sink and at each side of the sink base cabinet. The full weight of the sink needs continuous support.
Cut the Opening from the Bottom Side
Use a jigsaw with a medium-cut blade. The blade cuts on the up stroke, so do all your cuts from the bottom of the countertop to minimize chipping. Be sure the cutout is supported when you reach the end of your cut so you don’t break an edge. After the hole is cut, set the sink into the opening to check the fit. Do a bit of trimming if it binds as you drop it in.