Many humans believe that slith language consists of no more sounds than a hissing lizard makes. Nothing could be further from the truth. The classical slith tongue actually depends on extremely clear pronunciation both of consonants and of vowels. It is true that it contains a wealth of fricatives and prefers the unvoiced forms, but it also has many other sounds.
Long vowels are indicated in one of several ways. A macron, a circumflex, or a double vowel all represent a long vowel. That is, kālōs, kâlôs, and kaaloos are all the same thing. In very casual writing, particularly in the current day, long vowels are sometimes not indicated (e.g. kalos), but this is considered very colloquial and bad style for all but the most informal writing.
If short vowels are said to be held for a beat, long vowels normally are held for a beat and a half, although they may be held for as long as two beats or more, depending on the speaker and situation.
Note that semi-vowels i and u never assumed their consonantal qualities in the classical tongue. That is, i was never pronounced the same way as the y in English you, and u was never pronounced the same way as the w in English we. They were always separate syllables.
All stops are aspirated.
Rh should not be confused with gh, the fricative. Although they are allophonic in French and German, they are not the same sound, and sliths distinguished between them.
As above, gh should not be confused with rh, the trill.
Finally, some consonants occur in long forms. These are indicated with double letters. That is, hess should be pronounced with a lengthened sibilant at the end, with the same rhythmic implications as for long vowels (a beat and a half if a single consonant is considered a beat). Digraphs are written with the second letter doubled: a long sh is spelled shh.
Two short vowels in succession create a diphthong, never two separate syllables. No long vowel can be followed by another vowel. No long vowel can be followed by a long consonant (hence kālōs, not *kālōss). Neither can a long vowel be followed by two different consonants in a row. It is unusual, although not impossible, for more than two consecutive consonants to appear in a word.
Words are stressed according to a system of heavy and light syllables (exactly like Latin). A syllable is considered heavy if it has a long vowel or ends with two consonants (either a long consonant or two different ones). That is, both syllables of kālōs are heavy, because they both have long vowels. The first two syllables of hessāden are heavy, the second because it contains a long vowel, and the first because it ends with two S's. The first syllable of Nakhtha is considered heavy because it ends with khth, two consonants. The second syllable is considered light because it has a short vowel not followed by anything.
Words are stressed on the penultimate (second-to-last) syllable if that syllable is heavy, or on the antepenultimate (third-to-last) syllable if the penult is light. Thus baināden is stressed on the penult, but bainatas is stressed on the antepenult.
Stress is also not as strong as in English or French. It is more or less as forceful as in Spanish.