sand
砂 centers on sand: the granular material found on beaches and in deserts.
砂 combines 石 (stone) with 少, which likely contributes the sound and suggests smallness, giving the idea of small stone particles: sand.
The left side is stone 石, and the right side is few/little 少. Picture a stone broken into few tiny grains: that is sand.
For サ, imagine a sandy beach where you sit under the sun: sun -> サ, and the sand is warm beneath you.
sugar
sand; grit; fine gravel
desert
sediment; earth and sand
sandy beach
gravel; ballast; pebbles
landslide
double-lined fusilier (Pterocaesio digramma)
sandstorm
hourglass; sandglass
sandpit; sandbox
sand dune; sand hill
downpour; pouring rain; heavy rain; pelting rain; cloudburst
yellow sand; yellow dust; Asian dust; dust carried on high winds from Mongolia, northern China, and Kazakhstan
sandbar; sandbank; shoal
gold dust; silver dust
cube sugar; sugar cube
Sahara Desert
white sand
shirasu; white pumiceous soil of southern Kyushu