Depends on your goal. 12/12 from seed works with photoperiod plants and finishes fast, but you get a tiny plant, usually a few grams to maybe 20-30 g, so it's more of a challenge than a yield play. If you want a bigger harvest, keep her on 18/6 for 3-4 weeks and then flip. If you do the solo cup run, use a small pot, keep the light close enough for about 400-600 PPFD to make up for the short days, and don't overfeed. If she's an autoflower, leave her on 18/6 or 20/4, since 12/12 only cuts her yield.