You started with flat front cabinets because they were inexpensive and served their purpose, but now you want to jazz up your cabinet doors with trim moulding. Don't be afraid of this project. There are easy ways to add moulding to a cabinet that don't require complicated cuts and installation instructions. Take your cabinet doors to the next level by adding shaker-style trim. Shaker trim is attractive and easy to install.
Scrub the cabinet doors with ammonia-based cleaner and a soft rag to remove any oils or residue that might interfere with the glue.
Measure the width of the cabinet door at the top and the bottom of the door, using a tape measure. The two measurements might be off slightly if the door is not perfectly square. Cut a trim piece to match these widths, using a circular saw. Cut straight across the wood.
Sand the edges of the wood with fine-grit sandpaper to smooth out the rough edges.
Run a bead of construction adhesive along the back of the two trim pieces. Place the trim on the front of the door and attach them to the cabinet door with C-clamps.
Measure the height of the cabinet starting at the bottom edge of the newly installed trim piece downward to the top edge of the other newly installed trim piece. Repeat the measurement on the other side. Cut trim pieces to match these measurements.
Sand the edges of the cut trim to smooth out any rough wood.
Spread construction adhesive on the back of the trim. Insert the trim between the two previously installed trim pieces. Clamp the trim to the door. Allow the adhesive to dry.
Repeat this process with all of the remaining cabinet doors.
Drive finish nails through the trim and into the door to secure the trim to the door. Remove the clamps. Fill the nail holes with wood putty.
It may be easier to remove the doors from their original location before installing the new trim. Mark each door's original location to make the reassembly easier.