I dig an hole and stick them in. But i use the opportunity to ameliorate the soil.
At the beginning of spring, i do prefer to give them all the care I can, since i do recognize that the plant is incredibly stressed, and till the moment it starts to grow, pretty much anything wrong can kill it.
I suggest to avoid the excess of moisture till the temperature are high enough. Also keep in mind that the soil is cooler than the air at the end of the winter. I plant only if a couple of week of sunny, relatively hot time is forecast. And i water with water that has been heated by the sun, to give maximum heat to corm and roots (useless probably, but who knows).
I have done this only two times, so talk even to someone more experienced than me.
I would advice against planting too soon. I plant mine with daily temperatues around 17C and night temps at 8-10C. Dwarf Namwah and Orinoco do grow with such temperatures, but anything less seems dangerous on a stressed plant. Once you lose the pstem, game over.
Take a look here:
Dwarf namwah overwintered with the bigdog method