Trim the asparagus to remove woody ends. You can leave the spears whole or cut them into smaller pieces if desired.
Bring a pot of water to a boil. Add the asparagus and blanch for 2 minutes for small spears or sliced asparagus, 3 minutes for medium spears, or 4 minutes for large spears.
Promptly remove the asparagus from the boiling water after it's done blanching, using a slotted spoon or tongs, and submerge in a large bowl filled with ice water. Let it sit for a few minutes to cool and to fully stop the cooking process.
Drain the asparagus and pat dry. Try to get it as dry as possible to prevent ice crystals from forming in the freezer.
If freezing whole spears, place them in a single layer in a freezer bag. Label and date the bag. Freeze for up to 6 to 8 months.
If freezing asparagus pieces, you can add the optional step of flash freezing them first. Spread them out in a single layer on a baking sheet lined with parchment paper. Place the tray in the freezer, somewhere it won't get bumped, for 1 to 2 hours until frozen solid. Transfer to a freezer bag. Store for up to 6 to 8 months.