Everything in a Bouquet Garni is in stick or stem form so they can be tied together without cheesecloth, and it's easy to remove the bundle when finished.
On a clean, flat work surface, lay an 8-inch piece of kitchen twine. On top of the twine, in the middle, add carrot, celery, leek, parsley stems, and thyme sprig. Tie the bundle into a knot to secure.
Add to the pot and simmer as directed in your recipe. For easy removal, keep one length of the twine long enough to tie to one of the pot handles. Remove and discard.