How to Finish the Corner on a Countertop

Dry-fit both the laminate countertop sheets over the L-shaped cabinet where you want to install them. The sheets overlap along the middle where you have to form the miter cuts.

Clamp the laminate countertop sheets to the cutting table, ensuring their ends overlap at the point where you will form the miter. Align the sheets so their outer corners meet at the same point.

Cut a square scrap of plywood diagonally in half so it forms two triangles. Set one triangle aside, since you only need one for the inner corner. This triangular plywood serves as a cutting guide that ensures the adjacent edges form a tight, seamless fit.

Clamp the plywood triangle to the cutting table, flush against the inner edges of the overlapping sheets. If required, butt the inner corners of the sheets against the plywood triangle. Remove the plywood when the inner and outer corners of the overlapping sheets match up.

Place a straightedge diagonally over the upper laminate sheet so it extends from the outer corner to the inner corner. Using the straightedge as a guide, draw a straight, diagonal line on the upper sheet with pencil.

Grasp the trim router fitted with a laminate cutting bit and guide it along the marked line on the upper sheet. The trimmer cuts through the overlapping sheets, forming a miter cut.

Bevel the lower side of the cut edge of each sheet with a gentle swipe or two of the sandpaper. Place the straightedge on the L-shaped counter and draw a diagonal line over it that extends from the outer corner to the inner corner.

Spread a thin layer of contact cement over the backs of the laminate sheets and the countertop substrate using a paint roller. Let the cement dry to the touch.

Set wood dowels every 12 to 15 inches across the substrate. Lay one of the laminate sheets over the dowels.

Align the mitered end of the sheet against the line n the substrate before pressing it in place, starting from the outer edge and working your way to the inner edge. Remove each dowel as you press the laminate in place so it adheres to the adhesive. Repeat the process with the adjacent sheet, ensuring its mitered edge butts tightly against the edge of the previous sheet.