Spinach is one of the veggetables that gets caught in your teeth most easily.
Spinach is one of the vegetables that really gets caught between your teeth.
この場合、次のように言うと自然な感じで良いですよ。
ーSpinach is one of the vegetables that gets caught in your teeth most easily.
「ほうれん草はすぐ歯に詰まる野菜の一つです」
one of the vegetables that ...「…な野菜の１つ」と most ... で「最も…な」を使って「代表格」を表現すると自然ですよ。
ーSpinach is one of the vegetables that really gets caught between your teeth.
「ほうれん草は本当に歯に詰まる野菜の一つです」
このように really「本当に・実に」を使って強調し、簡単に言ってしまってもいいですよ。
ご参考まで！
Spinach is a classic example of a vegetable that is likely to get stuck between one's teeth.
Spinach is one of the representative vegetables of those most likely to get stuck in one's teeth.
ご質問ありがとうございます。
① "Spinach is a classic example of a vegetable"＝「ほうれん草は典型的な野菜の例です」
"that is likely to get stuck between one's teeth."＝「歯の間に引っかかりやすいものとして。」
② "Spinach is one of the representative vegetables"＝「ほうれん草は代表格の一つです」
"of those most likely to get stuck in one's teeth."＝「歯に最も引っかかりやすい物の。」
ご参考までに。
カナダ 
アメリカ合衆国 
