Bring a large pot of salted water to boil and prepare a mixing bowl with ice water.
Wash the carrots under cold running water, scrubbing away dirt as needed. Trim the carrots, remove the skin with a vegetable peeler (optional), and slice them into ½-inch circles.
Add the carrots to the boiling water, and cook for 2 to 3 minutes. If you are using whole, baby carrots, blanch them for 5 minutes. Remove them with a slotted spoon and immediately add to the mixing bowl with ice water to stop the cooking. Let them sit in the ice water for a few minutes. Add more ice as needed if most of it starts to melt.
Drain the carrots, then arrange them in a single layer on a baking sheet lined with parchment or wax paper. Place the baking sheet in the freezer (somewhere it can fit without getting bumped or moved). Let the carrots freeze for one to two hours until frozen solid.
Transfer the carrots to a freezer bag, leaving ½-inch of head space, and seal tightly. If you are using containers, leave 1 or 2 inches of head space to allow the carrots to expand. Store for up to 12 months. Use directly from frozen in hot dishes, such as soups, stews, and casseroles.