Place the Formica sheet on a solid work table.
Measure and mark the cut lines, using a tape measure and pencil.
Place a straight edge along the cut line on the side of the line that has the longer section of Formica.
Clamp the straight edge and the Formica to the tabletop at both ends with C-clamps.
Remove the casing screw from a utility knife with a flat-head screwdriver. Open the casing and insert a plastic/laminate blade into the slot. Screw the casing back together.
Run the blade along the straight edge to score the cut line. Use firm pressure and work slowly and carefully to keep from running off the cut line. Score the cut line twice.
Lift up on the shorter side of the Formica until it snaps apart. Smooth the Formica edge with sandpaper or a file, if necessary.