1/4" spiral bit. A downcut for pocketing would be preferred, as well as a 1/4" compression bit for part cut out.
1/16" router bit. Not required if you want to use a chisel to cleanup the pocket in the left and right sides instead.
As stated in the description, this is based on the Cleat Systainer Shelf :
Use the instructions shown in the link above if you want to create locking disks.
Use a regular 1/4" bit or compression bit to cut out the parts first. Then use a quarter inch regular bit or downcut bit to clear the pockets. Change the pocket to an inside cut, and cut the inside. Doing it in this order with a downcut bit will prevent chipout when cutting out either the Two Base or Four Base.
Cut the pockets on the left and right sides to a depth of 1/4". Cut the pockets on the bases to a depth of 1/8". If you have a 1/16" bit, you can use it to cut the dogbones in the left and right side pockets, otherwise use a chisel to square up the corners at the back part of the pocket.