I had a student ask me about words that end in I-L-D. Let's break it down. We have child,
wild, mild. These all have the [aɪ] diphthong, then Dark L.
To make the dark sound, the tongue tip stays down.
The Dark L is made with the back part of the tongue pressing down and back. Child.
Then the tongue tip can come up for the D. Child. Wild. Mild.
But I-L-D can also be the [ɪ] vowel, like in build.
Same Dark L, tongue tip down. Build. This is the same as the word guild,