There are about as many ways to route handles into a cutting board or butcher block as there are species of wood available to make a cutting board. I am going to share my method with you below. This is not the only method, probably not the best or quickest method, but this is what I have found to work well for me and my work flow with cutting board construction.
I use one simple piece of wood with a notch cut out of it as my jig.
With this one simple jig I can cut two different size handles by simply using different router bits. A bowl bit with no bearing is used with the router inside of the jig “bouncing” off the walls. A bowl bit with a top bearing is used for a larger handle with the bearing riding the wall of the jig. If I ever found the need (which I haven’t), I could make a different size jig to give me another two handle size options with the same two router bits.
To use the jig, I center it on the board and clamp it down to secure both the jig to the board and the board to the bench. I then begin routing the handles in a counter clockwise direction. I typically take around 4-6 different cuts to arrive at my final depth.
You will get some router burn, I don’t care what bit you’re using or how sharp it is. The best way to minimize this is to take a shallow final cut and then get to sanding!
The depth of cut is a function of personal preference, proportions to the board, and function. This one ended up being around 5/8″
There you go, these handles are quick, easy, and look pretty good if I do say so myself!