Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.

Americans pronounce sphere as SFEER (/sfɪr/). You'll hear it in sentences like "The engineer interfered with the sphere".
Record yourself saying "sphere" 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.
Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.

Lift your bottom lip to touch the very bottom of your top front teeth. Blow air through this contact point without voicing.

Start with the high 'ih' position. Pull the tongue back and up while flaring the lips slightly.
The textbook way isn't wrong — it's just not how anyone actually says it.
Americans use a relaxed retroflex R — the tongue curls back rather than rolling. The R is one continuous sound with the vowel before it, not two separate sounds.