Fill a huge stock pot, preferably fitted with a basket insert, with about 4 quarts of water. Keep in mind that when you add the solid ingredients the water level will rise, so don't fill the pot up more than 1/2 way. Squeeze the lemon juice into the water, tossing in the halves too. Add the bay leaves, salt, seasoning, onions, and garlic; bring the broth to a boil over medium-high heat and simmer for 10 minutes. You want a very aromatic broth with plenty of salt and spices; taste it, don't be afraid to make it strong so some of that flavor can penetrate and get absorbed by the potatoes and stuff.
Add the potatoes to the pot to give them a head start and simmer for 10 minutes. Now add the corn and sausage; cook another 10 minutes, making sure everything stays covered with the liquid. Toss in the crawfish and shut off the heat. Cover the pot and let the crawfish steep in the flavor for 15 minutes. Drain and spread the crawfish, sausage, corn, potatoes, and onions out on a table that's covered with newspaper. Serve with lemons, hot sauce, and plenty of napkins.