The creators of written languages with alphabets separated consonants from vowels. They did so for the sake of simplicity and efficiency. The 7 graphemes a, e, i, o, u, p and t generate more than 40 different syllables. Other languages are not so efficient, having completely different signs of each syllable. In such a language, “at” and “it” would, in their written forms, bear no resemblance to each other. The proliferation of different signs for each syllable creates an additional burden on the learner’s memory. Alphabetic languages have greatly lightened this load.
However a contradiction between the written and spoken forms has developed. You see, it is a property of written signs, that they can be isolated, i.e. written outside a word on a page. However this is not a property of all speech sounds. Consonants can not be spoken in isolation, existing only as part of a syllable. So how then to we isolate something which can exist only in a context? It seems a bit like trying to separate oxygen from hydrogen without eliminating water.
The trick is to maintain the same consonant, while changing the vowel. Assuming that you are using chart that looks something like the one below there is a clear procedure to follow.
a u o i e
Firstly, ensure that the learner has consolidated the vowels sufficiently, such that when pointed by the teacher they are spoken spontaneously, without doubt or pause for though. Next tap /e/ then /t/ and say /et/. Next tap /at/ and wait for the student to say /at/. If this is correct, tap /it/ and wait for /it/. Continue with the other vowels.
Thus the students have shown through practice that they are able to isolate the consonant component of a spoken syllable and transfer this into a different syllable. This is a skill acquired in the crib, as a baby learns to speak its mother tongue. We are simply applying this skill to the written form, or rather, showing how this skill can be represented symbolically by signs made on paper.
In the written form consonants develop a relative independence which contradicts their true nature in the spoken form, but which conforms to the logic of an efficient writing system. This has misled many educators, but need not have.
Consonants are isolated by varying the vowel component of a syllable, not by removing them from the syllable. This is the linguistically correct approach to introducing, eliciting and practicing a consonant.