When my timer beeps at me, I scoop it out of the pot. Use something big enough that scooping doesn't take long. I scoop because don't want to toss that boiling water away as I blanch in small batches. When I scoop, it goes right into a pan of ice water. You need enough ice in it so that it doesn't all melt by the time the spinach has cooled down. And once it is in the water, stir. Cool the spinach down as fast as possible.
Once that block is frozen, I pop it out. If I'm freezing in the fall sometimes I get lazy and just put it in a zipper bag. But it is still spring and these have to stay frozen for a long time to last the whole winter. So I will vacuum seal these. I also store my produce in a chest freezer. Your typical freezer is a frost free freezer. It heats up the walls to melt the ice that forms. Produce doesn't keep in that kind of freezer very well before the quality drops. Maybe 2 months. But in my chest freezer I still have some of last year's produce and it tastes good. At least in the vacuum bags. In a zipper bag would be freezer burned by now.