If your spinach comes out of a packet and contains just the leaves, use as is. If the stems are intact, remove and discard the harder thicker stems at the bottom. Retain the thinner, more delicate stems close to the leaf. Rinse and set aside.
Fill water in a medium-sized bowl and add the ice cubes into it. Set aside.
Bring a large pot of water to a rapid boil. Add large handfuls of the spinach to the pot and tamp them down with tongs or a ladle until completely submerged. Turn them a few times in the water. Blanch for 2 minutes, then remove the spinach and add to the bowl with ice cubes. Repeat in batches.
Take handfuls of the wilted spinach from the bowl and squeeze out as much of the water as you can with your hands. Transfer to a kitchen towel and pat dry. Repeat in batches.
Divide the scraggly bits of spinach into a muffin tray and press down with your fingers. Alternatively freeze them in ice cube trays if you want smaller portions, or in a container.
If using a muffin tray/ice cube tray, transfer the tray to the freezer and let it sit for a few hours until the spinach is completely frozen. To remove the pucks, flip the tray onto a table or counter and tap down a few times until they fall out.
Transfer the frozen pucks straight away into a zip-lock bag and freeze. If there’s still a bit of moisture in the spinach, they might stick to each other a little upon freezing. But a gentle pull will get them apart just fine.
Once you take them out and thaw, don’t refreeze. Keeps well in the freezer for up to 2 months.