How do I make a large hole?

Whats the best way to make a hole larger than my largest holesaw?

You had to make two holes in the top - one large hole to pour, and

3M™ High Strength Large Hole Repair

How to Drill a Hole in Tile

Filling the Bead Hole Tutorial by Artwhim

Shelf standard makes superior step-and-repeat jig

Drill Large Holes in Ceramic Tile (10 Seconds!!!)

How to enlarge or align a hole in metal

How to prevent a veneer catastrophe

Hole Saw Trick (Making Holes Larger)