Try getting ready to say an ordinary English "l" as in "let's", but instead of saying the "l" hold your tongue where it is and let the air escape to the side of the tongue.

Oh, wait, you asked what it sounds like, not how to pronounce it. Your best bet is to buttonhole a Welsh-speaker and get them to demonstrate. And no, it is not like the Spanish "ll" to speak of.

Chinuk Wawa also has some other, more unusual consonants (though they're quite usual in Northwest Coast languages), particularly the "ejective" (or "glottalized") consonants, where basically you pronounce a glottal stop (the sound between the vowels in "uh-oh" and "oh-oh", or in some pronunciations of "bottle" [bo?l] or "battery" [bæ'ri]) at the same time you make another consonant. For example, the "k'" in "tumala nayka munk manak'i-Lush" is an "ejective k", where you get ready to say "k" and then do a glottal stop before continuing. And there's the combination "t'ł", which is similar to the click that many English-speakers use to call a horse, except the click is explosive rather than implosive. It's a combination of a glottalized t and a barred l. Fun to practice; hard to get fluent in.

Haruo