For this, I highly recommend going into 'Chill Marathon' mode in Effects mode.
Choose whichever level you like, as that doesn't matter. However, I do recommend having 'traditional colours' for the tetrominoes set in the game options.Make sure that the piece selection you have set when you start the game is 'Fixed', not Random. This will allow you to get an even distribution of pieces, and disregard bad RNG.
I recommend going for this combo with a four-wide valley, as you can see in my achievement video below: