Lashing is one of the skills that not all people know even though they should. It is simply the act of tying sticks to one another, and helped me out this past summer when I was making a table between two bunks. I don't profess to be an expert on the subject, but I do know how to lash.
All you need is twine (or rope) and two sticks. You may also want a knife to cut the twine.
Position the sticks like so...
Take the twine and, while holding one end of it tightly on the top stick, wrap it around four or five times like so...
Tightly wrap the twine between the sticks several times (now might be a good time to note that this is the same piece of twine, no cutting yet).
Cut the twine and tie both ends together to secure the lash. You're done!