Raise the back of your tongue to touch the soft palate. Add vocal cord vibration, then release.

Americans pronounce guys as GAHYZ (/gaɪz/). It's 3 sounds in 1 syllable. The vowel glides through two positions, not one fixed shape — keep both halves audible.
Record yourself saying "guys" and play it back. The mic stays on your device — nothing's uploaded.
1 syllable, 3 sounds. Explore each sound's mouth shape and how it's made.
Raise the back of your tongue to touch the soft palate. Add vocal cord vibration, then release.

Start with your jaw open wide and your tongue resting low and flat. Glide the front of your tongue up toward the roof of your mouth as your jaw closes halfway.
Same position as S, but add vocal cord vibration. Feel the buzz.
