Craftsman used to make a router crafter and this is how many folks have done what you see in that photo (that might even be the same device). There are variations of this, some DIY.
Those long grooves were made by standard panel bits that were common back in the days of metal bodied routers.View attachment 402239
Very new and found this pic on the site. Would love to make this and I have a router mill. Can anybody give me more details about bits needed for this project. I have five by five blanks.