Practice has two syllables with the stress on the first: PRAC-tice. The transcription is /ˈpræk.tɪs/, and it is the same in UK and US English. The vowel in PRAC is short and relaxed, like the a in cat.
Mouth movement sequence
Start PRAC with the jaw slightly open and the tongue resting low, so the vowel is short and relaxed.
Let the tongue tip tap lightly behind the top teeth for the t in -tice, then slide straight into s with no vowel added.
Keep the second syllable short and quiet, a quick tiss sound; saying pracTEES or practiss-ee are common slips to avoid.
Say it in a phrase, with a contrast
Say the whole phrase once: I need more practice. Keep the beat on PRAC and let -tice slip out quickly after it.
Compare it with a word that stresses the second syllable, like police. Say practice, police a few times. In practice the strong beat stays on PRAC; in police it moves to the end. This keeps your rhythm from drifting to pracTEES.
Try a question and answer. Can we practice tomorrow? Yes, let's practice. Say both lines, tapping the desk on PRAC each time.
Your turn: read Practice makes perfect aloud twice, stress landing on PRAC both times. If -tice comes out as tees, repeat the phrase slower until the second syllable stays short.