Routing Keyhole Slots
Here is the project, 17 half round and 7 round plaques to cut a keyhole slot on the back of to use as the hanger holes.

How to get them all cut in the same place ?
Using a piece of 1/2" plywood , cut a hole the width of the router base and  width ( plus slot length ) in length.  Leave some extra wood  around the hole as shown.
Cut a piece of clear plexiglas to fit the hole. Then with your keyhole router bit cut a slot into the plexiglas as shown.
Using a marker pen draw a line in the center of the jig and plexiglas as shown.
Using a square mark the center of the wood item to cut the slot into.
Now with the plexiglas in the hole lay the jig over the wood item , line up the marks on the plexiglas with the mark on the wood item. This centers the slot in the item. Adjust for the height location you want.
Hold or clamp wood to the jig and turn over.
Nail some temporary  cleats to the back of the jig, to use to index the jig on all the wood items of that shape to cut slots in.
Use different cleats for other shapes.
Remove the plexiglas layout insert.

Clamp the jig with the wood item indexed against the cleats to the table
Adjust the keyhole bit in the router so it will cut the slot.
     Set the router into the slot and tilt it up in the front so the bit is not in contact with the wood. Start the router and lower it into the wood , once in, pull the router towards you in the slot, back up to other end and shut off router, lift it out of starting hole.
The slot is finished. Unclamp this wood and set up the next piece against the cleats and clamp it to the table.  All of the items will be identical when done.

Easy wasn't it !