A trick to help with the offset washer relief. Drill from the bottom as red58 suggested but stop when the tip of the drill just comes through. Get a brad point drill bit to help with this part. It has a point that is long enough to see when it comes through. Then place the washer over the little hole. Center the square hole on the pinhole and trace around the washer. Draw two lines to establish the center of the washer. Use that center and a forstner drill to relive the washer. That way the center for the washer relief can be maintained. Then finish the hole for the bolt. There are other ways to control the forstner bit but the center point on the bit is the easiest way I know.

Steve H