[techhelpbb]

Toe clamp the block and a piece of sacrificial material to the machine deck.
Tab the flange so they do not float till after all the isolation is done.
Then cut them loose.

Use a standard drill to rough out the pockets behind the flange and around the tube.
Then finish it with an end mill.

If the inside is for bearings probably want to use a boring head.
If the outside is a critical dimension you might also be able to use a boring head.

There are other options.
Like using a lathe.