Cut a Dado in the Backsplash
Before you assemble the underlayment, plow a 1/4-in.-deep, 1/4-in.-wide dado into the backsplash (Figure A). The laminate slips into the groove to give you a little wiggle room when you install it. You can cut the dado by making a few passes on your table saw.
Raise the Countertops
Verify Sink Size
Cut the hole for the sink after the underlayment is installed but before you install the laminate. Most sinks require a 21-1/4-in. x 32-1/4-in. hole, but make sure you have your sink on hand so you'll know what size hole to cut. Cut the back side of the hole with an oscillating tool, and then cut the sides and front with a jigsaw.
Sand the Seams
There can be a small gap between the underlayment boards, but the seam has to be absolutely flat. Mark the seam with a pencil, then sand with 50-grit paper until the lines disappear.
Use a 'Slitter' for Narrow Strips
A laminate slitter ($140 at online retailers) is almost a must for cutting thin laminate strips. It has an adjustable guide, so you can cut strips ranging in width from 1/2 in. up to 4-1/4 in. Cut any narrow strips first, before rough-cutting the large countertop pieces. All the pieces will be cut a bit long and trimmed down after they're installed. Make sure you have enough of the sheet left over to cut the large L-shaped section.
Rough-Cut the Top With a Circular Saw
Cut the main top piece of the laminate with a circular saw. Use a board to create a space so the saw blade doesn't grind into the floor. Avoid scratches by sticking a few strips of masking tape to the underside of your saw base. The front side of the laminate will hang over the edge and be trimmed off, so your cuts don't need to be perfect.
Glue the End Caps First
Cut the end cap so the bottom portion and the very top are close enough to be cleaned up with a file. The rest will be trimmed with a router. Cut the end cap to size with snips, then paint a thin layer of glue on both surfaces. Let the glue dry just until it's no longer wet to the touch, then carefully line up the top and ends and tip the piece into place. Embed the end cap by lightly tapping the whole surface with a smooth, burr-free hammer, and then it's ready for the router.
Scribe and Cut the Top Cap
Before you get your first whiff of glue, make sure every piece fits. The top of the backsplash will need to be scribed and trimmed down. Use a small silver marker to scribe the top, and then carefully cut it with tin snips.
Make Small Cuts
To avoid cracking the laminate, don't cut more than 1/4 in. at a time. Clean up the edge with a belt sander.
Use Tin Snips
Tin snips are a good tool for cutting the scribed line.
Trim Excess Laminate in Place
Install the front edge flush with the bottom of the underlayment, and set it with a hammer. Then trim off the excess with your router. A compact router with an offset base is a must-have when you're building countertops in place.
Apply the Adhesive With a Scrap
Clean all surfaces with compressed air before gluing up the top surface. Cover the perimeter with a brush and then grab a scrap piece of laminate to spread on the rest. Apply the glue on the underlayment the same way. It gets messy trying to glue the backsplash after the top is installed, so cover the backsplash with glue at the same time. And this stuff is a potent chemical, so always use an organic vapor respirator, open a window and turn on the exhaust fan.
Use Spacers to Install the Top
Laminate adhesive is sometimes referred to as “contact cement” because it sets as soon as the two coated surfaces come into contact. That's not necessarily a good thing when you're trying to maneuver a large, floppy sheet into place. Cut strips of leftover laminate and use them as spacers. Because the adhesive won't stick to the strips, you'll be able to slide the sheet around. Start pulling out the spacers once the top sheet is in position. Make sure the spacers are clean so they don't leave debris behind.
Smooth Laminate With a Board
Instead of using a roller to smooth out the surface, use a board wrapped in a towel. If a piece of debris does get in between the two surfaces, the soft rubber on a roller can indent around the lump and actually crack the laminate that surrounds it. Start on the back side and work your way out to the edges.
Trim the Backsplash With Snips
A router won't be able to reach the inside corner of the backsplash, so use tin snips to trim it down before you install it (make small cuts). That way you won't have as much material to remove with your file. Press the section on with a board the same way you did the top. The top cap piece is set into place with a hammer.
Trim Out the Sink Hole
Use your router to trim the hole for the sink. Just poke through the material with a spinning bit and work your way to the edge. Right before you finish the cut, support the scrap material so it doesn't fall down and tear out the last little section.
Once all the pieces are in place, file all the edges, including the bottom. You can buy a file especially designed for plastic laminate for less than $20 online. Always file in a downward direction, never back and forth. Clean off excess glue with lacquer thinner or whatever solvent your adhesive manufacturer recommends.