This is a typical bit for this kind of cut.

If you are using a table router, carefully measure out on the edge of the plywood where the mortise will be cut. Mark it clearly! Use a piece of scrap wood the same thickness as your plywood.

Set the height and depth carefully so molding will fit inside of it. Your final product should look like this picture.

If you are using a hand held router, we recommend using a plunge router as shown in this picture. Although a smaller laminate trimmer could be used, we do not recommend it because it could put undue stress on the motor and tends to be less stable than the larger router.

This picture shows the cut being made with a large, hand held router. Again, we recommend using a piece of scrap plywood to set up.

This picture is the standard Osborne Wood Products, Inc. Table Top Molding.

Insert a sample piece of plywood into molding to make sure it fits well.

This picture is an example of the plywood sitting to low in the molding. This is incorrect and will need a lot of sanding later. A proper fit has the tabletop slightly below the top edge of the molding.

Here is an illustration of the plywood sitting to high in the molding. This is also incorrect (it is actually worse than the above) because you will have to sand down the tabletop, and you will most likely expose the plywood core (and that would look yucky).