Depends on what width your saw blade is compared to the slot width you require.
If they are suitable then I would suggest the following;
Set your saw blade to the height, (depth), you require for the slot. Clamp or screw a large board to your table width guage and set it at the correct distance from the saw blade. The large board will help prevent the door from tilting as you feed it through.
Practice with some scrap wood first, adjusting the stop until you know it is precisely where you need it to be.