I like to cut mortises and stopped grooves using the router table. Here’s my method for skipping the hassle of a time-consuming trial-and-error setup process.

After laying out the mortise or stopped groove, use a Forstner bit to drill a hole at each end of the mortise or groove. Then at your router table, drop one of the holes over a straight bit to set bit height, the fence position, and your first stopblock. Use the other hole to set the opposite stopblock, and you're set up to make the cut.
—Philip Extance, Bridgewater, Conn.