With a tape measure, measure the width and length of the two pieces of countertop to join. Note the measurements on a piece of paper.
Measure a 4-by-8 sheet of plywood to the width and length of the countertop. Cut your plywood to this size with the table saw.
Find the center of the cut piece of plywood. Draw a 45-degree angle on the face of the plywood using a pencil. Cut the piece of plywood into two pieces with the circular saw.
Position the two cut pieces on your cutting table to form the 90-degree angle of your countertop. Secure the pieces of plywood to the cutting table with clamps.
Place the pieces of laminate so they overlap the plywood on the cutting table. Align each edge and then clamp in place.
Place a straight edge from the outside corner to the inside corner of the 90-degree angle. Draw a line on the laminate with the pencil.
Cut the laminate along the pencil line with the circular saw. Sand the cut edges of the laminate with the sandpaper.