Prepare the broccoli: Wash the broccoli under cold running water to remove dirt and debris. Optionally, soak it in a saltwater solution for 5–10 minutes for a thorough clean. Cut the broccoli into evenly-sized florets, about 1–2 inches wide, and slice stems into smaller pieces if freezing them.
Blanch the broccoli: Bring a large pot of water to a rolling boil. While the water heats, fill a large bowl with ice water and set it aside. Add the broccoli florets to the boiling water and blanch for 2–3 minutes for florets or 3–4 minutes for stems.
Cool the broccoli: Using a slotted spoon, quickly transfer the blanched broccoli into the ice bath to stop the cooking process. Let it cool completely for about 5 minutes.
Dry the broccoli: Drain the cooled broccoli and spread it on a clean kitchen towel or paper towels. Pat dry thoroughly to prevent ice crystals from forming during freezing.
Pre-freeze (optional): To keep the broccoli from clumping together, spread the dried florets in a single layer on a parchment-lined baking sheet. Freeze for 1–2 hours until firm.
Package for freezing: Transfer the pre-frozen broccoli into freezer-safe bags or airtight containers. Remove as much air as possible before sealing to prevent freezer burn. Label the bags with the date.
Store in the freezer: Place the packaged broccoli in the freezer. Frozen broccoli will stay fresh for up to 12 months.