At its best:
Place crocks in the base of a large terracotta pot and half fill with good quality, peat-free compost.
Space out the corms 3-4cm apart, planting right up to the edges of the pot to make full use of the compost surface.
Top up the pot with more compost and lightly firm. The finished surface should be just below the pot rim.
Water in well and place the pot in a bright, warm spot outside. Keep the compost moist by watering regularly.