Reply by MrRon

I want to go against the grain and suggest a 3HP router, template for the holes/locations, and 1/4 carbide bit.
The template could include all the holes AND the spacing so locating the next hole to cut would be a snap.

That just my two “bits” worth as I am a “routerholic”!

Or, how about a CNC …. ?

- oldnovice

If doing a large quantity, I d also recommend a plunge router.

You can also use pegboard form the big box store to make a jig.

1) Attach a small square of pegboard to your router base.
2) glue a couple short 1/4” dowel pegs through the holes of the small square in step 1
3) use a bigger piece of pegboard as the template. The pegboard holes are 1/4” round and spaced exactly 1” in each direction.

The picture shows a homemade metal plate for the router, but it can be done with pegboard too.

You can also use a smaller router bit and use this method to make holes for adjustable shelves.

- Rentvent