This needs 3/4" stock, a 1/8" regular bit and a 2.5mm bit that can cut at least 16mm

First cut the "topcut" part that will cut out the basic bricks from the top.

Then put a scrap piece (3/4" or so) to cut the "workholding" file; this will create a shape into which you place the half finished bricks from the previous step for 2-sided cutting. Make sure they fit very snug; use paper as a shim if there is any slack.

then -- while keeping the machine zero -- put the brick in upside down and cut the "bottom cut" file for hollowing out the bricks.