Disassemble the vanity with a screwdriver, taking off all the knobs, hinges and hardware. Lay out the particleboard pieces on a flat work surface.
Run a vibrating pad sander over each surface that you’re going to relaminate, enough to dull it. Wipe up the dust.
Measure the dimensions of the first section of particleboard. Transfer these dimensions to a piece of laminate, using a pencil and square, adding an inch all around the perimeter.
Cut out the laminate at the marked lines, using a razor knife. Pull the wax paper off the back of the sheet. Press it onto the surface so it overhangs all around by an inch.
Press a laminate roller over the whole piece, running the roller in overlapping courses to squeeze out all the air.
Use the razor knife to cut off the overhanging veneer from the edges.
Repeat the whole process for each part of the particleboard that has to be relaminated. Put the piece back together.