So you want to grow sunflowers indoors, that's a great idea. First, you'll need to start with a decent sized pot, at least 6 inches deep to give the roots some room to grow. Fill it with a good quality potting soil and plant the seeds about an inch deep. Make sure your pot is in a spot that gets plenty of direct sunlight, ideally south facing. Keep the soil moist but not waterlogged, and once they're about 6 inches tall you can start giving them some fertilizer. Also, keep in mind that sunflowers can get pretty tall so you'll need to provide some support, like a stake or a trellis, to keep them from toppling over.
