The easiest way would be with a 1.5" Forstner drill bit. Much simpler than a router and much faster. The Forstner bit has a spur point so that if you measure your spots and use an awl to make a starting hole to locate the bit it will be more than accurste enough. You can make a scratch on the side of the bit with the awl once you have the depth you want so that you can get all the depths the same. That's if you are drilling by hand. Setting the depth on a drill press makes it much simpler.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.