I've had good luck using "speedbor" flat spade bits.  They are boring normal flat bits but there's a cutting tang on the outer edge of both flats, and they work to cut the circumference loose before the main cutting edge lifts the swarf out.

[![enter image description here][1]][1]

Not a brand recommendation, there are plenty of examples at your average bigbox store.

  [1]: https://i.sstatic.net/l45gP.png