I sow my lily seeds two times, asiatics and seeds I'm not sure if they will germinate in January, and trumpets and trumpets x OTs late January/ early February since they grow faster. All my seeds are sown in pots, one cross in each pot.
When the seedlings starts to get their first true leaf I start to give a weak dose of fertilizer in the water.
My experience are that when the seedling have one or more true leafs they survive when transplanted. I usually transplant my seedlings in April.
My seedlings are transplanted in these boxes.
After the leafs have died back I plant them out in the garden.