It can be hard to safely control narrow workpieces, like drawer sides or faces, when you have to rout dadoes or dovetailed slots across the grain. But a simple sled like this, with toggle clamps mounted to a scrap fence, gives you the added stability needed.
I made the base of my jig from a 3/8″-thick, 12″ x 18″ polyethylene kitchen cutting board. A 3/4″ or 1″-wide slot, routed down the middle, enables me to use the sled on my router table. Install a guide collar in your router table that matches your sled’s slot width, to control the cutting path.