It is technically called a voiceless lateral fricative pronounced by placing the tongue as for pronouncing L, and then pressing out voiceless air at the side of the tongue, like a very noisy whispered L. My Icelandic teacher called it "a hiss at the corner of the mouth", and Welsh teachers apparently describe it by saying that the Welsh name Pwll sounds like if you say the English words _push_ and _pull_ simultaneously. Actually "shlan" would be a pretty decent approximation of _llan_. Another approximation is "fl" as in Floyd, which is an Anglicized spelling of the Welsh name Llwyd, and the _thl_ in _athlete_ also comes close. The Icelandic spelling _hl_ in a word like _hleypa_ 'leap', also gives a pretty good idea, but as I said it's rather noisy, so again "shleypa" or "thleypa" should come even closer. The Xhosa language also uses the spelling _hl_ for this sound.