Using a sharp knife, slice off the root end of the leek.

Turn the leek around and slice off the top 1"-2" of the dark green end.

Find the spot where the bottom white/pale green portion of the leek transitions to dark green and slice the leek across at that intersection.

Take the bottom white/pale green portion of the leek and slice it in half lengthwise.

Now, cut each half into thin slices making half circle shapes.

The same can be done with the dark green portion of the leek if using (although it's typically discarded) but it's best to keep these two portions separate as they have different flavor and cooking times.

Clean the leeks by placing the half circles in a salad spinner or bowl of water and letting them soak. Swoosh the leeks around with your hands to release any dirt from the leaves so that it settles on the bottom.

Scoop the leeks out with your hands or use a slotted spoon. Transfer to a kitchen towel to drain and pat dry before using as desired.