Hi, You don't say what hardiness zone you are in. Lacking that info I will assume the ground freezes where you are. If you are in a warm climate any Lily you plant will not grow again unless they are frozen EVERY year for 6 weeks Minimum. In that case you will need to dig them up and freeze them. If you need to do that they need to have somekind of soil or peat covering them. Don't just put them in a bag and in the freezer.
Generally if you get at least some snow they can be left in the ground. Planting depth is not super critical with Lilies. It is better to plant them too shallow rather than too deep. Lilies have the ability to pull themselves down by their roots to the right depth. If you leave one on top of the soil it will grow. The reason to plant winter hardy bulbs 4"-6" deep is to protect them from the HEAT of SUMMER not from the cold. But 4 inches is good. They are very tolerant of soil types but not clay. Lilies can stand dry or soaking wet ground with ease. I do NOT water my Lilies ever unless there is no rain for 3 weeks. During dry periods they do well anyway. If you plant 3 bulbs you will have 24 in 3 years. The color varieties are anything you want except blue or black. I think there is a new blue one. They come in sizes from 6 inches tall up to 8 feet tall. Flower style is just as varied with out facing, upward, downward, single, double petaled. Some have 2 blooms some have 100. Some have small (BB size)bulblets growing on the stem near a leaf. Those can be planted and will be mature size the 4th spring. Some grow new bulbs under ground around the parent bulb. If you leave them where they are you get a nice group but after a few years the parent will die so it is a good idea to move the "babies" a few inches. There are types which grow "baby" bulbs on top of the parent and others under. The outer "flakes" can be pulled off and planted HALF into the ground. They will mature in 3 years too. I love the beauty of Lilies. I'm not talking about Daylilies which are ROOT plants. Flower size runs from 2" to 10". The Orientals generally have the most scent and most of those are pinkish and white. I like the Trumpets. You can search for your own varieties. Liles are great because they are so tolerant of how and what you plant them. Don't get too fussy. By the way....your potted Easter Lily most likely was 24" tall or close to that. The ONLY reason they are that short in the pot is because the growers spray them with a growth retardent to keep them short and from falling over in the house. Planted in the garden they will be 4-5 feet tall. Have a nice day