From the inside of the cabinet, add the L-shaped brackets. This will require two screws for each bracket.

One can add as many brackets as they want until they feel the desired secureness is fulfilled.

Ensure there are brackets and screws on both sides.

Utilizing a power drill, drill the screws into the side of the cabinet and on the bottom of the countertop.

Repeat this process several times, depending how many brackets there are.