Okay, take many flasks of alchemist's fire and prepare nothing but explosive runes as your 3rd and above spell slots. Cast these on either many or one flask. You could get a handy haversack and decide which to pull up at what moment.
Each ER does 6d6. If you put a whole bunch on a single flask, it will explode with very potent damage, no save.
If you are not allowed to put multiple ER on one surface, you can empty the flask, put the ERs on quarter strips of paper, roll them up, and stuff them in the flask with a single ER on it. When you toss it, that flask blows, destroying each piece of paper, releasing a score of ER.
You only need to throw the flask into the same square as the target because that is reading distance, so no save.
Using just 3rd level spells, a fresh wizard can get 18d6 as a touch attack, no save. But you can easily roll a 100d6 at high level. Good stuff!
Now, you said go for quantity, not efficiency. There are your ridiculous numbers of dice under epic levels.