This removes any bugs, dirt or anything else that may have come from the garden. I fill up the (clean) sink with water and use my hands to swish it around.
Step 2: Blanch the spinach
Blanching is not strictly necessary for freezing spinach but it does help it wilt down and pack easier into the muffin tins and in my experience it does help it keep longer. I have frozen spinach both with and without blanching and they are both great methods. If you are mostly going to use the spinach in smoothies, I wouldn't bother blanching it.
To blanch the spinach, bring a large pot of water to a boil and submerge the spinach in the water for 2 minutes. Remove from the boiling water and place in a bowl or clean sink with ice cold water to stop the cooking process. Place in a colander to drain or lay out on a clean tea towel.
Step 3: Pack the spinach
I love using silicone muffin trays to freeze spinach. I take a handful of leaves, squeeze them to remove as much liquid as possible and then place in the muffin tray. You can also chop the spinach before freezing which is what I do if I'm freezing larger spinach leaves. If you don't have silicone muffin trays you can either freeze the spinach in snaplock bags or make pucks and freeze them on a baking tray lined with baking paper or a silicone baking liner.
Step 4: Freeze the spinach
Place the spinach in the freezer overnight or until frozen and then transfer from the muffin trays to a large freezer proof container or snaplock bag.
Spinach will be good in the freezer for about 3 months. It will keep longer but will start to lose flavour and may begin to get icy.