These seeds will plant and grow themselves, so you don't need to plant them perfectly. Just cover them lightly with soil, and they will grow for you.

Lilium tigrinum is native to Asia. According to Gray's Manual of Botany they rarely if ever produce seed in North America.
The black things that you see in the leaf axils are bulblets not seed. I've never tried to grow lilies from bulblets. Since Tiger Lilies have spread and naturalized so easily I suspect that they are easy to propagate that way.
Sam

My mother used to poke a shallow hole in the dirt with her finger tip, drop in the bulblet and cover it with dirt. Plant them the way they grow in on the plant; the part that is attached to the plant is the bottom of the bulblet.

"I suspect that they are easy to propagate that way"-- an understatement! :)

mine fall off. i do nothing and have little lilies growing everywhere. i pull a lot!