level, small
扁 centers on something flat and thin: a level surface or a small, compact object. The idea of being flat connects both the 'level' and 'small' senses.
扁 is thought to combine 户 (door) with 冊 (writing tablet) inside, suggesting a flat, thin object like a signboard hung on a door. The exact historical development is uncertain, but the component combination fits the meaning of flatness.
A door (户) with a flat writing tablet (冊) hanging on it: the tablet is level and small, just like the meaning of 扁.
For ヘン, imagine a hen pecking at a flat, level surface: hen -> ヘン, and the hen's beak makes the surface flat.
almond
flat
tonsil
framed picture or motto (usu. horizontal, hung over gates or lintels)
flatfoot; flat feet; splayfoot
circular flat stoneware flask
squamous cell carcinoma; SCC
oblateness
lichen planus
flat shape
flatworm; platyhelminth
Platyhelminthes (phylum of flatworms)
amygdala; amygdaloid nucleus; corpus amygdaloideum
peritonsillar abscess; quinsy
tonsillectomy
almond oil
tonsillitis
tonsillar hypertrophy; enlarged tonsils
tonsillitis
peritonsillar abscess; quinsy