Select a straight strip of wood that is free of knots and uniform in grain and color.
Put on the safety goggles.
Select a router bit with a profile matching the desired profile of the custom molding. The whole bit does not necessarily need to be used to cut into the wood and it can cut in any amount.
Fit the router bit into the table mounted router according to the instructions provided with the router.
Adjust the router bit up or down to get the appropriate height above the table. The amount of the bit above the table will be the amount cutting into the wood.
Adjust the backstop to allow the desired amount of the bit to cut into the wood.
Plug in the router and run the strip of wood through the cutting area per the instructions provided with the router.
Turn off and unplug the router.