Select Single Player,
Set Enable Items to Yes,
Set Start Level to 14,
Set Game Mode to 100,000.
You don't have to play too cleanly as you'll want some junk on the board to combo. Don't play the long game and build up a long chain, match smaller groups where you can to try and raise/keep your sequence going.
will Hard Drop the piece. If it isn't part of your normal play style you don't need to use it. I'm mediocre at the game and did this in 30 seconds by lowering the pieces with