You do not say how often you need to attach and remove the disk nor how concentric or repeatable the process needs to be.
The magnets is a good idea, but may have too many degrees of freedom. If you bore a shallow recess, the diameter of the table, in the underside of the disk, you assure concentricity (but not repeatable clocking).
The blue tape and supeglue is good for a one off where concentricity is not important.
The blocks and screws is reasonable for both so long as you number the blocks and use the same screw holes.
Sand three rectangular blocks to fit the T-slots (width and height). Put a couple of sheets of paper under them so they stick slightly above the T-slot. Glue the disk to them with a heavy weight on it until the glue sets. It is a one-off challenge to make the disk concentric but after that, so long as you mark one block and one T-slot, it will always go back concentric and in the same clock position.