To prepare the spinach first remove any tough stems and then wash.
Bring a large pot of cold water to a boil. In the meantime, set up an ice bath.
Once the water is boiling, add the salt (1 teaspoon per L/qt of water). In this case, the water should taste a bit salty as the spinach can withstand it.
Blanch the spinach for about 2 minutes (you may have to do this in batches). Using a large, slotted spoon or spider, transfer the blanched spinach to the ice bath to cool.
Once cool, remove from the ice bath. Squeeze as much of the excess water from the spinach as possible. You may find it helpful to squeeze small handfuls of spinach in paper towels.
Note: You can also put the spinach in a colander and place something heavy over top to squeeze out the excess water. Leave overnight in the refrigerator.