Use a large pot to cook the leftover crawfish.

Coat the bottom of the pot with some leftover spices such as shellfish boil or crawfish crab. If you want, you can create a homemade blend of spices by using mustard seeds, pickling spices, black peppercorns, dried hot red pepper flakes, celery seeds, ground ginger, dried oregano, bay leaves, sea salt, and dried chives.

Add a small amount of water into the pit and put a steamer basket on top of the pot. Make sure that the liquid is not touching the bottom of the steamer basket. 

Bring the mixture of spices and water to a boil.

Put the crawfish in the basket and cover it with a lid.

Steam the crawfish for about 4 to 6 minutes.

Use a pair of tongs to take out one crawfish and check if it’s thoroughly cooked through. If it hasn’t heated through yet, resume steaming the crawfish and check one every 30 to 45 seconds to make sure that you don’t overcook it.  

Transfer the steamed crawfish on to a platter and enjoy!